He finally noticed.

Today, my boss finally noticed the prank. I brought him a cheesey "Moose Crossing" sign from Alaska, and it lives in his interior office window. But it's on a cheap suction cup, so it keeps falling down. We had a discussion about this and decided that the problems moose and squirrel are symbiotes, and the brain really lives in the squirrel, so that must be why the moose keeps falling down.

So at a certain point, I just had to aqcuire a picture of Rocky the Flying Squirrel and tape it to the moose sign. That that window is presently cornered between two tables, one of which is surrounded by rolling chairs. Thus the belly-crawling into the gap.

It took him till today to notice. And he was duly amused.