Unexpected outcome

[Hattifnatt]

Was clearing a bonus at Party when this hand came up...

After the river was out there i did't expect to get the money...

Party Poker No-Limit Hold'em, $ BB (10 handed) converter

BB ($20.83)
UTG ($54.67)
Hero ($50.45)
UTG+2 ($87.12)
MP1 ($116.6)
MP2 ($41.08)
MP3 ($50)
CO ($27)
Button ($47.5)
SB ($51.1)

Preflop: Hero is UTG+1 with 3[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/heart.gif[/img]. CO posts a blind of $0.5. SB posts a blind of $0.25.
<font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $4</font>, <font color="#666666">6 folds</font>, SB (poster) calls $3.75, <font color="#666666">1 fold</font>.

Flop: ($9) 5[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $3</font>, SB calls $43.45.

Turn: ($55.45) A[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>

River: ($55.45) K[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>

Final Pot: $55.45

Results in white below: <font color="#FFFFFF">
SB has 3d 4d (one pair, kings).
Hero has 3h 7h (one pair, kings).
Outcome: Hero wins $55.45. </font>