Odd issue with disappearing photos using Sandisk cards

Not 100% what is going on. On 2 separate occasions I have taken photos with my cameras using Sandisk Extreme 32GB cards (Sold by Amazon not 3rd party). The photos show in the camera and then when I put the card in my PC, the card is blank or shows photos I shot the last session after opening in Bridge. They aren't there at all. I put the card back in the camera and they are not there, but I see the old photos. Happened a few weeks ago using my 6D and again this morning using my 7D MkII. I threw away the SD card the last time this happened so this is a different SD card and different camera. The odd part is that I formatted the card this time in camera, took about 15 pics, put the card in my PC and the card only has the last files that I shot last session and deleted via the format. I know sometimes in Bridge the last photos still show up if you didn't close bridge and you have to click your SD card drive again to update, but that wasn't what happened. I put the card back in my camera again and the only photos were the one from the last time I shot. I took 5 more photos and those showed up fine in camera and on the PC this time. I've shot numerous sessions in between these 2 odd ones. Any idea what might be happening?

Do you know what happens if you put a card into one of the cameras, do an in camera format and then shoot say a dozen images and then attempt to review all the images in camera? (Without removing the card)

This is what I did this morning when it failed. I formatted in camera. Shot about a dozen pics. I reviewed a few of them in camera. (I didn't review all the pics though, just some of the ones I had shot) Turned the camera off, pulled out the card and put it in my PC and then only files on there were the ones I had just deleted via the format for some reason. I spent the $40 and bought Sandisk's recovery program and it recovered the files that I had shot that were missing. It's strange because it works fine for many sessions then all of a sudden has a failure like this.

carpenter wrote in post #18926785
This is what I did this morning when it failed. I formatted in camera. Shot about a dozen pics. I reviewed a few of them in camera. (I didn't review all the pics though, just some of the ones I had shot) Turned the camera off, pulled out the card and put it in my PC and then only files on there were the ones I had just deleted via the format for some reason. I spent the $40 and bought Sandisk's recovery program and it recovered the files that I had shot that were missing. It's strange because it works fine for many sessions then all of a sudden has a failure like this.

Note the text I've changed to red. This sequence makes me think you are not really formatting in camera, at least not the low level format that is commonly available in a Canon DSLR. If it has been low level formatted, then no older images would be available to be seen without some recovery utility. In addition, you do not delete via a format operation; you simply delete with the trash can key.

I personally have never had issues with using the camera delete although I know some people do not recommend the operation. In addition I always do a low level format (from the Canon menu). I also do not simultaneously use any given card between my two cameras (60D & 80D). That is not recommended, although I suspect it doesn't matter much with both cameras being the same manufacturer.

I again suggest another test. Put a card into a camera, do a low level format (you will lose everything), fire off about 12 to 15 images slowly, then attempt to review all the images while the card is in the camera. Then power off the camera, remove the card and check the images in the PC.

Definitely do not use the same card between different cameras.

I definitely formatted the card. I watched it go "busy" when formatting and then back to the "format" screen. When I said "delete via format" I probably should have said erased. Same routine I've done in 13 years of shooting digital so it's very odd. Absolutely no idea how or why the old files reappeared. With the 6d, when it happened, I didn't format in camera. I just stuck the card back in the 6d with the files from my last session. (maybe 15 pics). So, different camera, different SD card it seems that the issue could be with the computer/Adobe?? Though I have no idea what could possibly delete files upon inserting the SD card into the built in reader. I've tried 5 times now to replicate and cannot. Same with the 6d. I shot 4 more sessions after that happened without issue using that same routine I always use.