ukrm

i started a world in tekkit classic in single player and was working well through it. until a little while ago when i decided to move my world to a server just long enough to show my friend around. when i did all of my items were gone from my inventory, including a ton of iron, coal dust, some weapons and tools, but that's beside the point. after deciding to move it back into singleplayer everything stopped working, redstone engines wouldn't move even when powered, pipes were gone, all of my machines were broken and even when blocks are replaced they still don't work. does anyone know any way out of this problem? if there's some sort of back up of worlds stored anywhere? any help at all would be greatly appreciated, i've never had any problem like this before, even when moving worlds around like i did.