NL25 - 99 on T high flop vs unknown

[reemas]

villain is unknown. comment on all streets please.

Poker Stars, $0.10/$0.25 NL Hold'em Cash Game, 5 Players

BTN: $23.15
SB: $19.20
BB: $24.65
UTG: $40.75
Hero (CO): $25.95

Pre-Flop: 9[img]/images/graemlins/club.gif[/img] 9[img]/images/graemlins/heart.gif[/img] dealt to Hero (CO)
UTG folds, <font color="red">Hero raises to $1</font>, BTN calls $1, 2 folds

Flop: ($2.35) T[img]/images/graemlins/diamond.gif[/img] 2[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $2</font>, BTN calls $2

Turn: ($6.35) 2[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">Hero bets $4</font>, BTN calls $4

River: ($14.35) T[img]/images/graemlins/spade.gif[/img] (2 Players)
Hero checks, <font color="red">BTN bets $16.15 and is All-In</font>, Hero ?