To Johnny
Now, let me start out by saying that I don't know whether this is real or not. I'm undecided, and I hold no bias. You implied that you abhor camera phones, you are engulfed in a city that houses millions, and that this woman may even simply be on vacation, all of which suggests to the reader that you may never see the woman again. All of this makes it easier to simply drop the subject if this were a hoax. Second, although you have nothing to gain by not lying except for the attention, I don't believe you have any reason to simply make something like this up. I don't know you well enough to judge your integrity. For know I'm going to assume that your sighting was genuine.
With that said, here's my comment:
I believe I speak on behalf of everyone here when I say that you should continue to keep your eye out for this woman. I know that goes without saying, but stick with me on this one

Should you ever see her again, by any chance, I encourage you to engage in a conversation with her. If not to glean any information for us, do it so you can meet a wholly remarkable woman. Introduce yourself. Admit that you've seen her before and that you admired her assets. Ask her if she'd mind you asking a few questions about her (please excuse my poor grammar and lack of synonyms). I'm sure you have some of the same questions we do: Who is she? Where's she from? What size, exactly, are her breasts? Did she have large breasts when she was younger? When did her breasts begin to grow so large? Are they still growing? Does she know if it's a medical problem, or if it's just hereditary/natural growth? How is her day-to-day life effected by the size of her bosom? Does she have any interesting stories about her breasts (I have a friend who swears her tits saved her life once)? Is she single? Would she mind meeting you again sometime as a friend? And, one that we're most interested in, would it bother her if you took her picture?
Now, even if you don't get any info that the rest of us are dying to hear, at the very least you'll be given the chance to meet a fairly interesting person. Everyone has a unique story to tell, and I'm sure she's got a number of them. Sorry if I come across condescending or mean or any number of negative ways, I simply have this habit of over-rationalizing things. If my true-to-life experience experience was all I had to go by, I'd believe that anything larger than double-Ds would be a myth.