Concerning your feelings of guilt for using the ignore features available to protect yourself, quite simply put, you have no reason to feel guilty. The guy was acting aggressively and you are perfectly right to put your safety and comfort first.
As for this second guy you talked with who seems to have disappeared, at the moment he's not around and it doesn't seem your relationship was that far along. While he may have things in Life (Do people have a life off the computer?), I certainly wouldn't be insulted if a person I was talking with decided to continue on without me.
One of the best things I've done for myself is to stop looking for an online dom/sub thing. Instead, what I've done is surround myself with friends who are in the Life so I can grow without pressure. As much as some would talk about training and such, I think all of that will fall into place naturally. Sometimes online things work out, sometimes they don't. I don't mean to completely discourage you from looking for an online Master, just suggesting you might have an easier time looking for a Dom who will first be a friend.

- Mark