Illegal Stance - Help!

I was working on a creative map in LAN mode with my brother, when he stupidly chose to teleport me and input too high a number. The server kicked me out and since then has been giving me an "Illegal Stance" message. Unfortunately I don't have a back-up of the map itself. I don't know if this is a common problem, since I didn't find anything in the search bar, but I should very much like to be able to get back into this map! Please help.