Sometimes, a transaction shows up in my online bank statement that I can't identify. This is nearly always because it shows up as an address instead of a business name. Most credit charges show up by name, but debit charges sometimes just say "1234 Street Drive."
Today, balancing my checkbook, I saw a charge for $15 or so from 2106 Union Boulevard. I thought this was the diner, at first, but dinner at the diner was more expensive, and clearly right below this charge. I couldn't remember what it was, and I no longer had the receipt in my pocket.
I fired up maps.google.com, plugged in the address, and squinted at it. I saw the red roof of a pizza hut, and the marker was just a few blocks to the left. The only parking lot as bit as the one under the marker is at Blockbuster, but I haven't rented a video in months. It had to be the comic shop next door! With that, I remembered that I had bought Invincible volume three this weekend.