The thermal imager saved me from searching for the bees in this stucco wall. Entrance was below so I didn't know how far up the wall they went to start.
I went on a cool morning and was able to pick up the heat they produced. Very tiny colony, well, tiny because most of them were killed off from being sprayed!
The stucco wall was thick. My guess was about 1.5 to 1.75 inches thick. Could be thicker.