https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-ash3/c122.0.403.403/p403x403/523166_502966706381580_1927667765_n.jpg
I fixed my invisible Sim who appears to be underground by edit town and going to that lot and exciting then saving b/c when you edit a lot the Sims normally go on the side walk or home so that fixes them
or I get my Sim to watch the performance so I learn the Sims name then go to their house move them from their house to the clip board and back in, removes that Sim from being stuck :( although if you don't see that Sim stuck I am afraid I don't know what will happen to him or her :(