What to do when the river counterfeits your kicker?

[nut case ace]

At first this hand seemed pretty straightforward, but then I started thinking about the river and wondering if there is any value in just checking behind.

Party Poker 10/20 Hold'em (9 handed) converter

Preflop: Hero is UTG+1 with A[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img].
UTG calls, <font color="#CC3333">Hero raises</font>, MP1 calls, <font color="#666666">4 folds</font>, SB calls, <font color="#666666">1 fold</font>, UTG calls.

Flop: (9 SB) A[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/diamond.gif[/img], 2[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, UTG checks, <font color="#CC3333">Hero bets</font>, MP1 folds, SB folds, UTG calls.

Turn: (5.50 BB) K[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
UTG checks, <font color="#CC3333">Hero bets</font>, UTG calls.

River: (7.50 BB) 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
UTG checks, <font color="#CC3333">Hero bets</font>, UTG calls.

Final Pot: 9.50 BB

Not much of a read on UTG but after the flop and turn calls, i'm almost positive he has AT or worse. Then again, my reads aren't always perfect. Since the river killed my kicker and any ace will do, a river bet seemed pointless after some thought. Is there enough of a chance that he's been sandbagging this whole time or that he somehow had a 5 to warrant a check? Conversely, is there enough of a chance he limped with some small PP to warrant a river value bet?