Why was he quiet when we were alone?

i met this guy, my friends best friend. and he was really nice and funny and we have a lot in common (we play the same sport and are both good at it I guess and were both really devoted to it, its like our lives) so when I was with my friend he kinda talked to both of us like "group talking" shall we say. and my friend and I and him started throwing around with our sticks and playing a little and he was fun there too. but when my friend left he kinda got all shy and quiet and ya. I don't, does that mean he doesn't like me or what?
Why was he quiet when we were alone?
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