My game froze and then the save disappeared from R4 Card?

So I was playing my Pokemon Diamond game on my R4 card on my DS Lite and it froze. So I switched my DS off, because, you know, what else was I going to do? When I loaded it up again, it froze on the white screen that comes up right after you click on a game on the R4 menu, so again, I switched it off.

This time when I opened my Pokemon Diamond game, it loaded up fine, but instead of going to the game's menu, it began the new game sequence.

I, of course absolutely flipped, because I actually had another issue where I lost my save file, but managed to get it back, earlier this month.

So I put the micro SD card in to its USB and plugged it in to my computer, and it there was a .sav file on the card, but I don't know if it's my one or what. But it's not registering it.

Please, please, please help me. I've spent four years working on this game, after my first, original one that I had got deleted, and I have Event Pokemon, which can not ever be replaced. Every other Pokemon can be caught again, but not the event Pokemon. Please tell me there is some way to salvage my game.