We are having something replaced in our flat, and the guy who came to measure up and quote arrived just as I was about to go on the school run. He was from a national company, uniform, I had his contact details and obviously head office of said company would know who they'd sent on the job etc. I said did he mind if I popped out to get the kids for 10 mins while he measured up? All fine. Mentioned this to a friend at pick up (in response to her asking if I wanted to take the kids to the park after school) and she was horrified I'd left him at my house without me?! 
Maybe it too trusting, but seriously, what was going to happen? Maybe different if it was someone completely unknown with no traceable contacts e.g. Someone from a buying and selling site e.g. gumtree...
So AIBU to think it was totally fine to leave him?!