Why is my supervisor giving me a cold treatment ? Is he being possessive? What should I do?

I am a student working on a thesis with him. At this conference, someone introduced me to a potential recruiter. We start having a chat (in a group of 4) when my supervisor walks into the conversation, and then apologizes for interrupting. He never does this usually, so I am thinking that he sensed something. He then left, and the recruiter, myself and the person that introduced us moved to a different area to discuss the possibility. Later, guy that introduced me and I walked towards a lecture room, from where my supervisor was leaving. He barely said anything + accidently slammed into someone else.
For the rest of this conference (a 4 day event), he was acting odd and ignored me completely. The night that this happened, we all went to a party where he didn't even say hi to me, and so I also ignored him completely. Am I in trouble and is he being possessive?

Additional Details
Not married or interested in him. Just don't know where else to post this question...suggestion

What dose your background hold of?

Ever though of that

He sounds like the typical prick. He is just mad because you came in and took all his thunder. You are not in trouble you are in a excellent position. You are now superior over him and he is embarrassed about it. People don't like to be left out after being the main attraction for a long time. He could also be mad that someone else introduced you and not him.

To be honest, I don't really know. But my guess is that he see,s the others as competition and doesn't like it, He knows he can't say anything because he would be out of line and so ,, he goes into mope mode... Be careful, you live your life, don't let others guilt you into things you know you shouldn't do