I prefer to check it down if I'm on a draw to both ends, but if someone is betting in front of you and you have pot odds, you have to call it down here.
21 outs out of 44 cards is basically a 50% chance. You simply got unlucky.
Oh, btw, if you had 9 outs to the nut high, you had 9 outs to scoop at least 3 quarters of the pot, and FIVE outs to scoop, assuming your opponent doesn't make a boat.
You have game. I played you that 1 time at Empire, and you looked to play fairly tight. Maybe another day at the tables we'll see each other. I know you aren't a bank that sees every flop, I got an entire list of those buffoons.