Yes, I'm sure I'll get the hate comments from the agency people who will give me plethora of reasons why this is bad, wrong, or is the harbinger of the 2012 Mayan end of the world cataclysm ... blah blah blah not interested.

I've been seeing an agency girl for a while, we have a chemistry thing going on, and things are great. The agency has tried to steer me towards other girls when I found out later the girl I was looking for was working that day. So what's the best/most tactful way to bring up the subject, without creating drama?

and say here's my #, if you ever leave the agency keep in touch.
I am not going to lecture you because we both know that it is not accepted practice, but if we are going to be honest, it happens all the time. I have also been given private #'s in the past without asking for them.

She will either eagerly give you the # and email or report you to the madam or pimp. If the relationship is as you say ---- I think she'll give you the info you seek. This is not kosher in the biz, but is done all the time. The agency will ban you, and maybe out you on Blacklists if you get caught.  It seems odd to me that the agency steers you away from seeing her. Makes me think they may already be on to your plan.