I was building my factory in single player Tekkit wearing my nice gem armor using a red morningstar to mine out an area below it to place the machines. I quickly switched the hammer mode from 3x3 to single block to work on some details... or that was what would have happened if I actually had it selected.
What the key press actually did was use the offensive power of my gem armor and produce a big explosion at my current position which destroyed half of my machines and most of the walls, leaving an unsightly crater in the ground.
I know the map state got saved just a minute or so before that happened.
Next time that happens, is there any way to quickly leave the game without saving the new mapstate?