[Gerald]

Seems like a reasonable approach to me.
Maybe try just asking if they have any upcoming daytime appointments available. If you ask for a specific date and they don't have anything available they may not answer instead of just saying no.
I'd also include a "please feel free to reply any time as this is a private phone". Some providers discard messages if they are too old to make sure you don't get a response while sitting with your wife. lol
Maybe add a few more details like your age, ethnic background and how long of an appointment. Just don't ask for longer than one hour if you've never met her. Those guys are the highest rate of no-show and she doesn't know if you'll be fun or a lot of work. If it's less than an hour she may pass you over for a better income booking.
Anyone you do see from this site, use as a reference to see others so they know you are the real deal. Using your forum username also helps.
Maybe wait a week before trying again.