losing value on the river?

Reads: None, this is my first hand at the table.

Party Poker (6 max, 5 handed) converter

SB: $42
Hero: $25

Preflop: Hero is UTG with 7[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/heart.gif[/img].
Hero checks, <font color="#666666">2 folds</font>, SB calls, BB checks.

Flop: J[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>pot: $.75
SB checks, BB checks, Hero bets $1, SB calls, BB folds.

With only 2 others in the pot and one face card up I figured I'd bet my draw in hopes of taking the blinds or having a jack call so I can hit my flush.

Turn: K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>pot:$2.75
SB checks, Hero checks.

The king could have made SB 2 two pair and set up a check raise which I don't want to call with a weak flush draw, so I thought it would be best to take the free river.

River: 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, Hero bets $1, SB raises to $9, Hero calls.

When the heart came on the river I figured I'd value bet for a dollar and might get a call. The massive raise by SB had me worried, there was both a straight and flush draw on the board and my flush was not all that great. I just called hoping my flush was good.

My question is, how often do I see a higher flush overbetting the pot like this? Should I raise vs an unknown, or just call?