Makeshift striker Lee Bullen saved Wednesday's unbeaten record under new manager Paul Sturrock with a brilliant late leveler.
The Scottish centre-back was sent forward to partner lone striker Steven MacLean during a half-time reshuffle, and he responded with a point-saving strike.
Bullen headed a right-wing cross from defender Patrick Collins into the top corner six minutes from time - a goal Wednesday fully deserved.
Earlier a 21st minute strike from big targetman Clive Platt had left them heading for a first defeat since Sturrock took over in the Hillsborough hotseat at the beginning of the month.
Platt rose above defender Richard Wood and keeper David Lucas to head a lofted Peter Kennedy cross into the gaping net from eight yards.
Lucas had to be stretchered off with damaged ankle ligaments after being flattened by Platt in the process of scoring.
His replacement Ola Tidman was given a palm-stinging welcome moments after his arrival by a powerful Kennedy free-kick.
Wednesday were scarcely seen as an attacking force in the first period, but Bullen's switch ensured better was to come as they cranked up the pressure after the break.
He failed to capitalise on a glorious chance in the 55th minute when unable to make contact with a Glenn Whelan centre with the goal at his mercy - but Bullen went on to make amends in explosive fashion.
Wednesday captain Chris Marsden drilled a low twenty yard shot against the base of the post on the hour as the Owls poured forward.
MacLean broke free 15 minutes from time after latching on to a tame defensive header from Kennedy only to fire his single noteworthy chance of the night past the far-post.