If you never plugged your camera directly into your computer before, it probably started up one of the Canon programs (such as ImageBrowser) by default, which then started to compile a catalog of ALL the images on your computer.... hence the 33,000 images.
I doubt there is anything wrong with your memory card or that the images are actually lost.
It is not a good idea to delete images from a memory card unless absolutely necessary (i.e., running out of space and don't have extra cards). It is too easy to accidentally delete the better image or more than one image... and may even be possible to corrupt the memory card.
Best to download all your images to your computer, then use the larger monitor screen to sort through and delete the ones you don't want. That's much better/safer than trying to do it in-camera or with camera tethered.
I'd suggest you turn off ALL the "auto download" features you have set up on you computer, ESPECIALLY those in Lightroom or Elements.
Instead, use your computer operating system:
1. Before you even insert the memory card, set up a folder to receive the new images (however you organize your images... that's up to you).
2. Insert card in reader. If anything automatically tries to download the images, cancel it.
3. Navigate to and open the card in your computers OS... such as Windows Explorer or whatever Macs use now (I haven't used a Mac in about 20 years).
NOTE:I t's possible to set up your computer to do this by default, any time a memory card is detected.
4. Look for a folder on the memory card called "DCIM" and click on that (ignore the "MISC" folder you'll also see).
5. Look for a folder named something like "100EOS7D" and click on that (ignore the "EOSMISC" folder). You should now see a list of all the images.
NOTE: There may be more than one folder: "101EOS7D", "102EOS7D", etc. The camera automatically creates add'l folders when the file numbering system requires it. Be sure to check inside and copy from each, if there are multiples.
6. Highlight all the images (click on one to highlight it and then use "Ctrl A" to highlight all the rest). Then drag and drop them to the folder you created.
NOTE: In Windows, drag and drop using the mouse's left click button will automatically "copy" images.... while drag and drop with right click will bring up a menu giving choices... in either case, always "copy".... don't "move" images. Moving them removes them from the memory card and you don't want to do that yet. Copy leaves the original on the card, just in case there's a problem with copying them to your computer.
7. Let the system complete copying the images, then point Elements organizer to the images and tell it to import them (or however that's done in Elements... I use Lightroom and am using that terminology, but I imagine Elements is similar).
8. Once you confirm the images have been safely copied to your computer and have backed them up in whatever manner you use, it's safe to delete the ones on your memory card. I recommend you do that by using "format" in your camera (ONLY in the camera where the card will again be used... NEVER format in your computer or in another camera... this "prepares" the card for use in that particular camera). Personally I usually don't format my memory cards until I go to use them again.... The first thing I do whenever I swap a card into my camera during a shoot is "review" one image to be certain they are images that have already been copied off the card.... then when I'm sure, I format the card (some cameras... not sure about 7D... can do a "deep format" which takes longer. That's usually unnecessary... a quick "normal" formatting suffices).
Formatting in-camera doesn't really erase images. Instead it marks them as "okay to over-write". If you accidentally format, all is not lost. The images are still recoverable until you start using the card and sending new images to it. (Even then, it may be possible to recover images that haven't been over-written yet.)
All this takes far longer to write and read than it takes to actually do it. Using the OS data transfer method described soon becomes second nature and is pretty foolproof. There are just too many ways that "auto downloads" can screw up or be set incorrectly. I don't trust them!
Note: If you shoot JPEGs, you can see small thumbnails of them in Windows Explorer and can enlarge and view them in Windows Picture Viewer. But if you shoot RAW (CR2 in your case), those are not directly viewable, will appear with a "generic" icon on lists. HOWEVER, there are "codecs" you can install that make possible viewing thumbnails and even enlarging RAW files (unfinished, so color, contrast, etc. will be off... but useful to check focus, composition, etc.) At one time Canon had a codec they offered for free. I used it for a while on an old computer, but when I went to a 64bit operating system, it would no longer work and Canon didn't seem to have any interest in updating it. I've heard there are some other codecs available free from Microsoft and elsewhere, but AFAIK they are fairly restricted in what they can handle and I have no idea how well they work or if any of them are able to deal with Canon CR2 files.
I use a codec called FastPictureViewer. It costs all of $10 and allows almost every known type of RAW file to be previewed right in Windows, without having to open Elements, Lightroom, Photoshop, etc. It also allows direct viewing of TIFF, PSD and some other image file types that Windows can't normally "see". It has worked great with every type of RAW file (and others) that I've thwon at it and is well worth the money, IMO. I use it on three computers.
https://www.fastpictureviewer.com/codecs/P.S. If you need image recovery software, send me a PM. I have a bunch of licenses for Lexar Image Rescue that came free with memory cards I've bought over the years. Normally it costs about $50 for Image Rescue, but all you need to activate it is the license number (after downloading and installing from
http://www.lexar.com/support/downloads/). I have used it and it works. I only need one copy, so am happy to share some of the 8 or 10 extras I got for free!
If you never plugged your camera directly into you... (