Michael Spillane scored but was unable to prevent Luton from crashing to a 3-1 defeat at Southend as Junior Stanislas scored twice on debut.
The 19-year-old joined on loan from West Ham on Thursday and scored in both halves of the FA Cup second-round clash before James Walker claimed a late third.
Stanislas cracked a 25-yard shot into the top right-hand corner in the 34th minute with goalkeeper Conrad Logan rooted to the spot.
Luton were level 10 minutes from time when Spillane headed home although Laurent looked to have made a goal-line clearance but assistant referee Thompson allowed it to stand.
But the parity lasted just five minutes as Kevin Betsy's cross from the right was headed home by Stanislas from eight yards.
Southend wrapped up the win in the 90th minute when Anthony Grant burst into the box and teed up fellow substitute Walker who smashed the ball home from 12 yards.
