Well, I am an older (not elderly) gentleman, and I often meet women twenty or thirty years younger than me in restaurants.  I am pretty active on some of the sugar daddy sites, as are lots of attractive, young, local women.  And, since sugardaddy/sugarbaby relationships are not, at all, like provider/client meetarrangements,  meetings or "dates" often for lunch or dinner.  

And finally, I don't think it would be too cool to follow any young, attractive woman from a bar or restaurant.  Its sort of stalkerish, and besides, what would you say or do if you caught up with her?  "Hi, Honey, you don't happen to be a hooker?  Are you?"

My thoughts are, that if you want to meet providers stick with the normal channels.

the guy could be her Uncle.

As for the outfit, it would be EXTREMELY presumptuous to assume that women trying out new Spring outfits are providers, just seeing them in public.  Good providers dress discretely so that makes it even more unlikely.  Oh well, a guy can always dream.

As others noted, approaching her should you see her again would be a bad idea.  Just keep an eye out when you are looking through ads and maybe you will get lucky.

Green Mill Plymouth has very sexy ladies on Thurs and Fri on their patio in the summer..

Looks like the weather is starting to get warm up there!

Badboy...I agree with the others posted above.
Hope your doing well! Xoxo

Craigslist has a "missed connection" category in their personals.  You can post there, mentioning the day, time, and something to discribe the woman.  I don't think I would publicly ask, on Craigslist, if she was a provider.  But, if you are discriptive enough, someone might see it and respond.  At best, it is really a long shot.