I had a thieving boss like you one time. After a while I started to make sure after any meeting that everyone would get back the pens he had managed to get his grubby little mittens on.
Lol I was wondering if people thought I stole them! No they will be pens I find on the ground or other various ways, one of the ones I found in OP was at the beach. I have too much respect for the pleasure of a good pen to intentionally rob anyone of that lol.
You are doing good work protecting the pens! Your boss sounds really absent minded, like the lighter thieves I've known in my day haha.