Did I wimp out on the river?

Party Poker 0.50/1 Hold'em (10 handed) converter

Preflop: Hero is UTG+1 with 9[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/diamond.gif[/img]. UTG+2 posts a blind of $0.50.
<font color="#666666">1 fold</font>, Hero calls, UTG+2 (poster) checks, <font color="#666666">1 fold</font>, MP2 calls, <font color="#666666">3 folds</font>, SB completes, BB checks.

Flop: (5 SB) 6[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(5 players)</font>
SB checks, BB checks, <font color="#CC3333">Hero bets</font>, UTG+2 calls, MP2 calls, SB calls, BB folds.

Turn: (4.50 BB) 8[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, UTG+2 calls, MP2 calls, SB folds.

River: (7.50 BB) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks...

This was a loose and passive table. Basically, I didn't think I'd won the hand, I figured one of the remaining two players had an ace. I checked to limit the amount of money I had to put in at the end. Maybe they'd both check as well, and if someone bet, seeing the showdown would only cost me one bet. Surely anyone still in with an Ace would not have folded had I bet.