I accidentally did that to a provider once. It was several years ago and I was visiting New York. He was a super sexy Reiki provider. When we were done I was so completely relaxed that I left and forgot to pay I walked a few blocks and I was like "Oh shit, I forgot to pay him". So I called him up and said "I'm sorry, I forgot to pay you, can I run back to your place." I did and apologized again. He was so kind he told me, "I just thought you weren't going to pay me, but I was like whatever. If he doesn't he doesn't." He was so nice about the situation.