Under the current description of Escape Artist, stun and frozen should absolutely be covered by escape artist. Some clarification would definitely help as to what constitutes "immobilized".
I won't have to roll back, but my next couple of feats just got shuffled and changed if this is true.
Edit - And of course, almost immediately, I think I figured it out. "Immobilized" is when you can act, but not move. Stun and frozen (as well as incapacitated and mental breakdown) prevent you from acting as well, so they're not covered. I may be wrong, but this seems logical. Anyone more knowledgeable feel free to correct me though.