Think about it though: if someone wanted to really be anonymous, would he put in small hints on who he/she is through his/her anonymous monicker? Obviously not as it would totally be a bad idea. The S-N thing is likely just a coincidence.
Honestly it’s possible. We are all just humans. We are vulnerable and we are not invincible. More often than not, we don’t realize that we have made some slip-ups. Maybe it’s not his intention to leave a hint.
Although it’s also plausible that it might have been just a coincidence but there were some emails exchanged between them. Of course those could easily be forged but it all depends on us what we want to believe in.