Heynckes was unable to take his place in the dugout to see Robert Lewandowski equal his longstanding record of scoring in each of Bayern's first 11 home league games in a season.
The 72-year-old's illness did not stop him watching a 2-1 victory that leaves Bayern 18 points clear at the top of the table, however, according to Hermann.
"I think Jupp Heynckes was most engrossed in front of the TV," Hermann said.
"He texted me, I'll have to call him. Congratulations on the victory, he said.
"It was a very tough match for us. Schalke pressed very well, they were always alert.
"Congratulations to the team, what they've done over the last few months is very good."
Thomas Muller caught out Schalke goalkeeper Ralf Fahrmann from a tight angle to secure the Bayern victory after Domenico Tedesco's side hit back through Franco Di Santo.
But the modest Germany international claimed he was trying to pass the ball to a colleague.
"Our coach will say I cheekily put it in," Muller said. "I tried to square it.
"My hip was in a rather unhealthy position - and it just went into the corner.
"A keeper often guesses in situations like this, but I didn't have the time to see it and then score.
"I was a bit lucky indeed."