In no way do I mean to be rude, I'm just laying out the harsh truth. Here it goes...
I am in business for myself and there is a term business owners use for unwanted/unforeseen/uncommon expenses. It's called "The Cost of Doing Business" (CODB).
While your provider business is underground, it's still a business. Business is risky for everyone who owns one, underground or "legit".
You have to try to hedge against these unforeseen CODB expenses by charging enough per session, not living "paycheck to paycheck", and screening and keeping your eyes open for potential no shows.
Fact is, especially in your business, you are never going to be able to collect on your no-shows - plain and simple. And if no-shows are so common for you that you have to worry about them that much, then it's most likely a problem on your end or something you are not doing to minimize these no-shows. I guess you may also be doing business in an area with a lot of assholes that like to fuck with providers. It's possible. But nothing you can do about it in that case except close shop or don;t do business in such an area.
If you text or message a no-show telling him he owes you a no-show fee, he will never schedule with you in the future anyway (which is usually a good thing probably), but how are you going to collect then? Do you expect him to send you the money somehow? You may be successful with that 1 out of 1,000 times, but most of the time you will not be.
And stating that you have a cancellation fee on your website or your ads won't do anything because the first thing a guy is going to think when he reads that is..."ummm...OK. And just how do you expect to collect that, pray tell?"
In short, there is really noting you can do about it in this business. It's something you have to accept and try to minimize as much as you can.
SUGGESTION: If you get a no-show and you paid for a hotel room just for that no-show, it may be a good idea to post an ad out on various sites ASAP to see if you can get a bite on another client. That's what I would do if I was in that situation. In fact, when possible, it might be a good idea to always post an ad on a site anytime you secure a room for just one client that way you can make more money for that room you just secured. It's just a suggestion. I can't tell you wast to do and I di understand that sometimes it;s not possible for various reasons.