...as is strongly suggested in this post: https://www.reddit.com/r/Monero/comments/4z3ced/guide_to_using_monero_with_tor_correctly/
p2pstate.bin is stored in
~/.bitmonero on Linux and Mac. On Windows it's stored in
However, the gotcha in the link you gave no longer applies: the node ID is now regenerated at random at each daemon start. Therefore, deleting the p2pstate.bin file is not necessary for that reason. It might theoretically be used to fingerprint you based on the set of known peers, but that seems quite a stretch.