Ok so here's the situation. I have a number of SD cards that I have used with my drone and GoPro cameras over the past few years that have several dozen GBs of videos on them.

I have a relatively new MacBook that I bought a few months ago to do video editing and content creation.

Tonight I inserted one of the SD cards into the Mac to try and find a particular video file that I want to edit. Upon inserting the card, the Mac file manager showed me the correct video folder on the card, but the folder was empty. Strange I thought, but figured maybe it was a blank card or I'd previously moved the footage from that card elsewhere. All good, I just moved to the next card.

Insert next card - same result - video file folder there but no video files present.

Insert 3rd card, same result again. By this time I am starting to get concerned as I know I should have footage on some if not all of these cards. When I go back and check the properties of the cards, each shows dozens of GB used, yet all three cards are essentially blank with no media files at all (not even drone photos).

I then checked these cards on my Windows PC and same result. Folders are all empty, but "properties" show many GB used on each card.

I have two SD cards left which I have not inserted into the Mac, and these both show video files on the PC no problem - but these are not the videos I am looking for. So I know the video files I want are (or were) on one of the 3 cards that I inserted in the Mac.

I tried revealing hidden files on the cards by selecting SHIFT+COMMAND+FULLSTOP on the Mac as suggested online. This did reveal some hidden system files but no media.

What the crap have I done and how do I recover these video files that I know have to be there somewhere? The footage documents years of restoration of one of my cars and I'll be heartbroken if it's lost forever.