If it is a Tixati user then there's a high chance he or she is in one of Tixati's chat channels. You can try to reach out to them by making a forum thread (inside the Channel system, not here) and asking in chat a few times during the week. This is because many users have joined channels but are away from their computers.
Note: You may find new channels if you click "Gather channels". To find all of them execute this once a day.
It is technically not possible to contact someone through the peer ID or IP addresses. There were some old proposals to extend Bittorrent to allow chats and reviews/ratings but they're dead and not supported by anyone.