Striker Josh Windass opened the scoring for relegation-favourites Stanley from the penalty spot after 61 minutes after he was fouled by Smith.
He dusted himself down and blasted the ball into the bottom corner of the net before Smith made amends for his mistake when he slotted home the late leveller.
Smith did not know a lot about it as a long throw-in found Craig Mackail-Smith and his shot cannoned off Smith’s back and wrong-footed goalkeeper Jason Mooney with 91 minutes on the clock.
Goalmouth action was limited in the first half with Terry Gornell being denied by Elliot Justham and Nathan Doyle firing just wide for the Hatters.
Windass scored and Stanley should have increased their lead with Piero Mingoia, Terry Gornell and Anthony Barry all going close.
However, with four minutes of added time scheduled, John Still’s side went on the attack and Smith found the equaliser.
Paul Benson could have grabbed a late winner for Luton but his effort was blocked right at the death.