Volleyball...help!!!?

ok so i went to an open gym today which is like a practice before u tryout for that team.... i thought they would run drills and that but not at all.... the made group and scrimmaged group against group but u only played one certain position wen he asked in the beginning.... i said middle and he left me play it but sum people he was yelling at them saying they too short.... so we start played and this is about techinque and he expects us to like already no where we r supposed move on the court.... but its diff for every team... so i play middle... going up by the net to block when he on the other teams side and going to the ten foot line right when the ball come over and try to get the ball after the set.... we didnt really get much of a chance to play that much... he picked the best people from each group and it wasnt me... but i noticed people who even had that teams shirt on didnt get piked either... so they play and at the end he points to a girl ajnd says like shes the best one here.... i thought that was kinda weird... so i go to him and say thank you and he says your welcome and wait u need to work ojn moving back and forth and backing away from the net when your hitting but your hit and approach are good... er sumthing like that... idk...i feel like he already piked his team pretty much by picking the best people.... i really needgood advice and tips plz!!! thx so muchh!!!!