Lost worlds, as if deleted: please help.

[FTB_player]

Whilst playing on Feed the beast, It crashed and I re-entered Feed the Beast. But it said that there was a new version of Yogscraft so I thought "Oh goody, the left-out mods are being put in" and updated. When I entered all but ONE world was lost, which was reverted to the very start of when I was playing. I tried resetting to an earlier time to no avail. I checked the saves folder, and they were not there, as if they were *Gulp* deleted. Did the update create another folder and leave the old saves behind? Were they saved elsewhere and this update stop checking them (which would make sense, because of that older save)? and if so, the important question is: how can I, well, save them?

Please help, I am desperate!

 

[FTB_player]

Update: I have found them. they patently were deleted, but an earlier backup has kept them (still can't get my head round the reverted world). How should I go about moving them. Should I just move them to the folder and move the one currently there back? or is there a safer method? Also, How can I stop this happening again?