"But if they won't refund me I'm seriously considering going by myself. Is that lame?"

OH MY CHRIST, NO, IT AIN'T LAME. O_O I went to License To Wed by myself just this weekend cause my friends didn't want to go to that one, and the degree to which I was excited about that movie is nowhere NEAR the degree of excitement about Harry Potter. As long as there's no other reason for you miss it, I definitely say GO. \o/