I always tell the guys at my site to check the lavatories when their shifts are up. Several years back on one of my patrols, I encountered a trespasser in the executive Porta-Potty at a high-profile site I was working. Apparently he had been hiding in there for 2 hours and planned on making off with some valuable property. I zip-cuffed him and moved him to one of our holding facilities.
We managed to persuade him to sell out his friends who were going to help him, and kept them in our holding facilities until the police arrived. Long story short, checking the John prevented a high-profile heist that would have made national headlines!