Generally, the only ones posting UTR ads would be agencies.  What would be the point of an independent posting that she's available UTR?

Anyway, if you have credentials, references, or a history with the agency, you can often find out who the UTR is by contacting them directly.  If you have no history, or can't be verified, you're unlikely to get any info.  

This is all general.  Of course, some agencies may just tell you if you ask even if you aren't known to them.  

And, sometimes, one agency will announce an UTR, perhaps even listing hair color and measurements, and if you search here, eros, and agencies' websites, you just might figure out who it is because other agencies don't consider her as UTR.  For example, I know a number of women that BodyMiracle and other agencies consider UTR but Lita posts ads for them on eros naming them outright.  

Hopefully, this is helpful to you...