Accidentally deleted a lot of work and can't get back (completey ERASED from history)

I was working on an artboard and sort of keysmashed the wrong hotkeys (arround Shift Command X) and lost a full artboard and some history of work in another artboard, just disappeared and reverted to an arbitrary point of my history, with all that work COMPLETELY removed from my history. So I have no way of getting it back that I can find.

I think I might have hit some sort of hot key that deletes your history (for some useless unknown reason) OR it's a bug and my system freaked out. This has happened a few times to me. Does anyone know why this happens, so i can at least know what I'm doing wrong?