I assure you this most certainly isn't the first time this has happened since the BBS days, it happens all the time. Most places never tell the users about intrusions.
In fact, I'd bet most mid-moderately successful sites don't even know it happens to them. The hackers/spiders don't leave thank you notes behind (most the time
). You have to have some pretty keen eyes and/or software to spot the clues sometimes.
Deleting your account won't make any difference at this point. Even so, no one can do anything (at least here) with a regular user account that can't be reversed. However, if you would like your account deleted, let me know.