Thanks theymos! That's exactly what I was wondering. How did you do that? Was it with the 'bitcointools' that gavinandresen mentioned?
I output the most recent 10,000 blocks to a file (using the getblock patch) and then searched it for the hash (b5a1946b3...), which is derived from the BC address. This took only a few minutes once I figured out how to get the hash from the address. Tracking spends from that address would be more difficult, since you can't get the full public key directly from the address.
Making an easy-to-use web tool for doing things like this has been on my to-do list for a long time. People really seem to overestimate Bitcoin's anonymity...