50NL - Weird river spot with AQo

[thing85]

Villain is 32/12/3 over 172 hands.

Poker Stars, $0.25/$0.50 NL Hold'em Cash Game, 6 Players
LegoPoker Hand History Converter

SB: $48
BB: $76.20
UTG: $48.75
Hero (MP): $66.55
CO: $68.45
BTN: $14.65

Pre-Flop: A[img]/images/graemlins/club.gif[/img] Q[img]/images/graemlins/spade.gif[/img] dealt to Hero (MP)
UTG folds, <font color="red">Hero raises to $2.50</font>, 2 folds, SB calls $2.25, BB folds

Flop: ($5.50) 2[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/spade.gif[/img] A[img]/images/graemlins/spade.gif[/img] (2 Players)
SB checks, <font color="red">Hero bets $4</font>, SB calls $4

Turn: ($13.50) 5[img]/images/graemlins/heart.gif[/img] (2 Players)
SB checks, <font color="red">Hero bets $8</font>, SB calls $8

River: ($29.50) 5[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">SB bets $20</font>, Hero...?


What did he hit on the river? Or could this somehow be a slowplayed 2? WTF? What's my play?