25NL QTs flush draw backed into top pair

[derdo]

I didn't make my draw but backed into top pair. Am I calling the river bet?
First hand no reads.

No Limit Holdem Ring game
Blinds: $0.15/$0.25
7 players
Converter

Stack sizes:
UTG: $44.25
UTG+1: $24.50
MP1: $24.35
Hero: $25
Button: $1.60
SB: $6
BB: $16.70

Pre-flop: (7 players) Hero is CO with T[img]/images/graemlins/club.gif[/img] Q[img]/images/graemlins/club.gif[/img]
UTG folds, UTG+1 calls, MP1 calls, Hero (poster) checks, 2 folds, 2 folds, BB (poster) checks.

Flop: 6[img]/images/graemlins/club.gif[/img] 2[img]/images/graemlins/heart.gif[/img] 4[img]/images/graemlins/club.gif[/img] ($1.15, 4 players)
BB checks, <font color="#cc0000">UTG+1 bets $0.5</font>, MP1 folds, Hero calls, <font color="#cc0000">BB raises to $2</font>, UTG+1 folds, Hero calls.

Turn: 7[img]/images/graemlins/spade.gif[/img] ($5.65, 2 players)
<font color="#cc0000">BB bets $3</font>, Hero calls.

River: Q[img]/images/graemlins/spade.gif[/img] ($11.65, 2 players)
<font color="#cc0000">BB bets $4</font>, Hero ???.

Results:
Final pot: $19.65

[lacrymosa]

why not raise?