My job requires me to wear hi-vis (as well as other PPE) and it is crazy how little security pays attention to me in some of the very-big-name plants I visit, often with a laptop bag full of flash drives and a bunch of other tools that allow me to get into the machines.

Early in this part of my career, I found myself in a very large plant for the first time, and my escort got pulled away on some other task (I now expect this to happen since it's such a common occurrence), leaving me to fix the machine I was working on. The place was the size of a small town, and I needed to use the restroom, but nobody was in the vicinity to ask, so I did my best to follow the floor markings and signs. Found it, but took a wrong turn coming back and found myself in a completely different area. Since I was new, I tried to find my way back without asking anyone I saw because I did not want to look stupid, but nobody stopped me, questioned me, etc.

Probably one of the best lessons in social engineering is looking like you're supposed to be there.