It happened to me once, wait, actually twice.
First time, I was fairly new to this and got a hotel to see this provider who was coming to Fort Worth from Dallas. We had everything set up and before she left I told her the hotel. She texted me back and said "I don't do outcalls to hotels." Crap!
Second time, I had at least 2 verifiable references but had not joined P411. There was a provider I wanted to see so bad (she is now retired), emailed her my references, and waited...........and waited.......and waited.......til finally I emailed her to ask how the screening was going. She said the references had not contacted!
So I gave up, joined P411, went on a manwhore spree, got provider P411 ok's, then contacted her again. She never replied back!