Flopped bottom straight with flush draw on board

[BB_Specials]

1/2 NL

Hero is button with 7 /images/graemlins/club.gif 8 /images/graemlins/club.gif

MP 1 calls
MP 2 calls
Hero calls $2
SB calls
BB checks

flop
10 /images/graemlins/diamond.gif J /images/graemlins/diamond.gif 9 /images/graemlins/spade.gif

SB bets $4
BB calls
MP1 calls
MP2 calls
Hero raises to $20

SB calls
BB folds
MP 1 calls
MP 2 folds

Turn: 4 /images/graemlins/spade.gif

SB bets 26.70 and is all-in

This reeks of draw so I call

SB turns over 3/images/graemlins/spade.gif Q /images/graemlins/spade.gif

River: A /images/graemlins/spade.gif

SB wins the pot ($128.40) with a flush, Ace high


Is this guy a total donk, or am I missing something?