Have you ever forgotten the envelope?

I recently had a SW visit me for an outcall, and almost walked out the door while inadvertently leaving behind what was due. I chose to catch up with her before she left and hand it to her. I'm not sure if she would have realized what happened while driving away, later that night, the next day, or even at all had I not given it to her. To the girls: has this ever happened to you? Mind you, this is someone I have seen several times in the past. I'm not sure if she would have forgotten had I been a new client.