Guy started ignoring and pretending. Why?

Met a guy at bachlor party, when we were alone he asked for a date, and kissed me, I kissed back consenting to the date. He turned really desperate. I told him to slow down, I like to keep things slow and I don't go below the belt so soon. I'm not into one night stands or casual. Inspite of that he kept convincing and trying to turn me on. We decided on doing the next day. But next day at the wedding he acted like nothing happened and started avoiding me and even started courting some other girl, giving his coat to her and everything right infront of me.
Guy started ignoring and pretending. Why?
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