Don't forget to look in dresser drawers either. Mine always take the opportunity to jump in and we've closed many a cat in the dresser...even the barthroom drawers.

Even if you checked the basement, if you have one, did you check the attic? It doesn't hurt to look in places that you're sure she isn't in.

Pantry? You mentioned groceries...did you check in the fridge or freezer?
Under the bed, inside the box spring, or in the couch?

I'm sorry you haven't found her yet, but I'm glad to hear you're not giving up!