You're a regular, you'd have more info than most of us.  

Perhaps your text or voice mail or e-mail or tweet or whatever came to her at a busy time and she forgot to get back to you.  

Or she could have just taken a well deserved day or two off. Family emergency or just life.  
All kinds of possibilities...

If you've tried a few times to get in touch with her through various mediums, then it's probably time to leave her alone and if/when she wants to get back to you, she will.

Go see someone else and in a few weeks or a month or so, try her again if you can't get her out of your mind.

If you were a regular that she liked you would know how to get in touch with her.  Maybe you're the guy that jumped off the balcony of her studio without paying.  That story still cracks me up.

... there's no real upside to asking where is (provider name)?

If she can (and wants to) see you, she'll respond. I consider it part of the overall service/connection. If I've seen someone more than once and they don't respond even though they have recent advertisements, I probably would stop trying for a few months.

I don't take it personally at all or think badly of the provider - there are any number of reasons for a delayed response but no response at all? I move on as there are so many wonderful ladies out there.

That said, I haven't see anyone in months so take my view with a few pounds of salt!