my favorite story along these lines was the bug report for a browser that was submitted by an ex-wife/girlfriend. She became an ex when she discovered her SO regularly logged into dating sites. The bug was that she was able to get his login information even though she was not logged into his account.
I would think that your internet performance-enhancing-drug buying would be relatively safe from anyone other than law enforcement if you used one of the secure file deletion programs. Maybe he didn't even bother to delete anything at all.