So of course, after my last comment about bees getting in, I found a wasp in the studio today. It has since been relocated to the vacuum cleaner.
It may have actually been there since the workers were here and removing windows - it seemed to be partially stuck to something on the ceiling, and did not look pleased (although really, I've never seen a "happy" wasp). I hope that's the case, otherwise we've got some secret wasp entrance somewhere in the apartment, which is probably hidden in a spot we'll never find. Joy.