25NL: Button and Blinds.Turn brings trip 2's in BB

[EN09]

the SB is very loose and slightly aggro 36/7/2.5 with a wide range of hands played preflop. button is unknown and limps when folded to him, he recently sat down and this is his first button. his overcalling the turn as an "unknown" concerns me. is this founded or not?

i smooth called the SB figuring BTN would fold or raise with the hope he'd fold, and i'd get HU with SB. SB checks the river so i have know i have him beaten and being as i DIDN'T raise the turn, my river line is...???

EN

Full Tilt Poker, $0.10/$0.25 NL Hold'em Cash Game, 7 Players
LegoPoker Hand History Converter

BTN: $26.05
SB: $8
Hero (BB): $24.20
UTG: $5.80
UTG+1: $25.25
MP: $24
CO: $12.35

Pre-Flop: 7[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] dealt to Hero (BB)
4 folds, BTN calls $0.25, SB calls $0.15, Hero checks

Flop: ($0.75) K[img]/images/graemlins/diamond.gif[/img] A[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/club.gif[/img] (3 Players)
SB checks, Hero checks, BTN checks

Turn: ($0.75) 2[img]/images/graemlins/heart.gif[/img] (3 Players)
<font color="red">SB bets $1</font>, Hero calls $1, BTN calls $1

River: ($3.75) 3[img]/images/graemlins/club.gif[/img] (3 Players)
SB checks, Hero...???