Heynckes also scored in 11 consecutive home games for Borussia Moenchengladbach in 1972/73.
With barely five minutes gone, Schalke goalkeeper Ralf Faehrmann blocked Mueller's fierce shot, but Lewandowski was on hand to tap in his 19th league goal of the season to equal the record.
Franco Di Santo stunned the Allianz Arena by equalising in the 29th minute, burying his shot after Leon Goretzka miskicked from Breel Embolo's cross.
Valentino Lazaro scored two minutes before halftime.
"It was bitter to concede the goals, especially the second", admitted Faehrmann.
Well earned. It's good to have you back.
Mueller said it was a lucky strike.
"I am very happy with the goal and the win". The Germany worldwide started the game and lasted 70 minutes on his return after eight months out.
The 24-year-old netted twice on his debut against Cologne.
Mario Goetze, himself struggling in an injury-hit season, finished off a counter-attack by dinking the ball over Christian Mathenia in stoppage time for his second goal of the season.
Frankfurt defender Marco Russ headed the hosts back into the lead for his first goal since overcoming cancer in 2016.
Bayer Leverkusen dropped to fifth after slumping at home to Hertha Berlin 2-0.
Hannover ended Freiburg's nine-game unbeaten run with a 2-1 win at home to consolidate its midtable spot, level on points with Hoffenheim and Augsburg.