Some girls don't even offer same day appointments, and require you to book more than 24 hours in advance. What about the girl who is flying in to start her tour? If you know her first availability based on when she is checking into her hotel, I think that's about as good as you are going to get unless you think she shagged somebody inside the airport.
While the whole idea is unappealing, the fact of the matter is even if she hasn't had sex in weeks, some STDs can linger in the body for months without symptoms, and you could pick them up at any time. So if you aren't worried about STDs, then I guess you have to ask yourself whether you think soap and water will wash away traces of other people. If it bothers you, stay out of this industry and get into a monogamous relationship hoping your partner does not cheat on you.