Big Fish does indeed have some iPad games. Mushroom Age was more like a casual adventure than a hidden object game. Among the choices that Big Fish carries for the iPad, I would recommend:
Drawn: The Painted Tower
Drawn: Dark Flight
Azada: Ancient Magic
Nightmare Adventures: The Witch's Prison
Those four above have no standard hidden object scenes at all (except for one small hidden object scene in Nightmare Adventures, which is more of a wry joke than anything else, and quite amusing in its own right).
If you are willing to tolerate some hidden object scenes along with the adventure, I would also recommend:
Shiver: Vanishing Hitchhiker
Mystery Case Files: The 13th Skull
Mystery Case Files: Dire Grove
I hope you find something to enjoy.