Was zum Geier hatte dieser Gegner vor?

Party Poker 0.05/0.10 Hold'em (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: HTML)

Preflop: Hero is UTG+2 with 5s, 5c.
2 folds, Hero calls, 1 fold, MP2 calls, 2 folds, Button calls, SB completes, BB checks.

Flop: (5 SB) 9c, 9h, Js (5 players)
SB checks, BB checks, UTGC bets, MP2 folds, Button folds, SB folds, BB raises, UTGC 3-bets, BB caps, Hero calls.

Turn: (6.50 BB) 5h (2 players)
BB bets, UTGC raises, BB 3-bets, UTGC caps, BB calls.

River: (14.50 BB) 7s (2 players)
BB bets, UTGC raises, BB 3-bets, UTGC caps, BB calls.

Final Pot: 22.50 BB

Wenn er den Jack hatte, warum hat er dann zuerst gecheckt? Misclick? Sollte ich trotzdem 3-betten?