Bailey's second-half effort - a response to Leon Goretzka's stunning free-kick opener - snapped Bayer's run of three straight away defeats but Schalke perhaps deserved to win the encounter.
After a slow start, Schalke took the initiative with left-back Bastian Oczipka fizzing a shot just wide.
Encouraged, the Royal Blues poured forward and in the 34th minute won a free-kick, which Goretzka dispatched into the top corner with perfect aim.
A double substitution at the break paid dividends for Bayer on the hour mark as Jamaican winger Bailey found the back of the net with a deflected effort.
Lucas Alario - a northern summer signing from River Plate - then put the ball over the line to apparently give Bayer the lead, but much to Schalke's relief he was offside.