I have proof, in pencil and watercolor, that I came across a somewhat similar insect (the-other-one) when I was at school. It would appear that I had no camera at the time, and, I hope, no midterms either. The penciled remarks, meant to supplant the inaccuracies of the depiction, have long since been rubbed into oblivion, but I seem to recall that one of them stated that the beetle was more slender and graceful than the drawing made it appear:
I don't know how closely related it is to the creature I ran into last month, but it had an odd, jerky, and waspish gait to go with the waspish stripes.
*As I understand it, these are an East Coast species, but the pictures on BugGuide certainly resemble the one that got away (it's hard to forget the bright stripes, the reddish cast of the shell, and a beetle with legs quite that long). A quick search for a related West Coast species turned up an animal evidently related, but not at all the one I saw. Suggestions greatly appreciated, as usual.