The blogger who used my photo got back to me -- she said she spotted it on a Flickr stream used by a Seattle bike blog, Bike Hugger.
It's been picked up at least 3 times since then, including, most prominently, in this news item at Wired.com:
http://www.wired.com/autopia/2010/10...#ixzz128jU6TNA
From looking at the original Flickr stream, I can see that the photo was taken in September 2009 (not May, as I thought). The knee warmers in my pocket suggested to me it was on a day with a cool morning, and the fact that anyone was out taking photos on the bike lane made me think it was "Bike to Work" month, which is May. But I guess it was just a random September shot that ended up on Flickr....
Gosh knows how many people are admiring my backside the world over....