Running several characters at the same time was never a good idea. Yep, I accidentally deleted one. Or saved over it, whichever - 30 hours of play down the toilet. I think I've lost characters I'd worked on for even longer but I'd forgotten about it and wasn't as careful on the screen with the loads. Anyone else done this?
I think most people have. Someone made a suggestion that I adopted. Before you save go in to 3rd person view and rotate camera so you see the character, that has stopped me more than once form making that mistake (again)
I always double check if I saved over something or not, even if I know I didn't. I also keep my main character on one storage device while I keep the others on another one.