Even if his range is entirely Qs and he's betting for value, he'll have 4 QTs, 3 QJs, 4 KQs and 4 AQs. So worst case scenario we win 1/2 pot 20% of the time and full pot 27% of the time, giving us equity of around 37% equity (37.5% to be exact). Pretty easy call getting 3-1 and he doesn't even have to be bluffing the missed FD for it to be correct.