I get my checking account statement and see several charges that the thief made before I was able to get the card canceled. My bank cheerfully reversed those and I thought nothing of it.
Four months later, I see a charge on my statement from one of the same merchants as before. I called my bank, and they said that the merchant had authorized my card, but did not proceed to capture the payment until then. I asked why this happened on a canceled card, and was told the authorization happened before the card was reported stolen so they had to honor it. They told me the merchant had six months to capture the payment, and it basically was as if I had written them a check and they sat on it for months.
Clearly the thief had some buddy with a merchant account, and they were trying to see if they could sneak a charge in later without me noticing it.
I asked my bank if there was a way for them to see if there were more of these charges in the pipeline, because I had written some checks and it would be highly inconvenient to me if they bounced. They said they had no way of knowing. The only way to stop these from going through was to close the checking account, which would also mean the checks I've written were going to bounce anyway. So I just had to wait out two more months and hope nothing more happened.
Luckily, that was the only instance.