Sorry - shoulda thought of that.
Not surprising. Even a small amount of insecticide should work, given a little time.
Sounds as if your problem is solved.
I had a few wasps in my BBQ two weeks ago. I opened it up, placed a flaming newspaper inside, then closed it and walked away. About a hour later a few wasps were still hanging around, so I nudged them with what was left of the paper. When they were all gone I washed the BBQ and left it open so it wouldn’t be as appealing.