Not happened to me, but it has been close once. One girl said it had happened to her a couple of times.
Personally I'd go back and pay. If a regular I might ask if it was OK to pay on my next visit to avoid a special trip.
So what would you do?
I have forgot to pay a girl in Birmingham, I rang her to say I was coming back to pay her.
We can't criticise escorts who are scammers if we punters 'forget' to pay. We are paying for their time so if they have performed as discussed and there have been no issues, if you have forgot to pay or underpay always go back and pay them.
As many have mentioned though, this is a very rare scenario