Janitors usually aren't going to enter the bathroom and start cleaning until someone leaves as a courtesy. He was waiting a long time for Lendrum to leave, apparently much longer than a usual amount of time for someone to use the shower room. The janitor finally gets to go in and looks like no one actually used the facility, the shower floor is dry. he goes to empty the trash and there's this weird box sitting in there. I think I'd be a little curious if I was him. I don't think the janitor was sitting there keeping track of every traveler's comings and goings but he was just trying to get his job done. Although, I have a feeling that airport workers are at least a little bit trained to be on the lookout for drug/animal smuggling and human trafficking so the egg would have been a clear sign that something isn't right. I'm sure 99.999% of his job involves mundane cleaning but he's still trained just like everyone else to "say something if you see something".
I wonder if properly trained state sponsored OP's can see a flaw here? Not sure if it's down to dumb bad luck or not.
Analysing every situation you're in would be to draining, and not sure how you'd pre train.