The Stones' five-game unbeaten was ended by their Kent rivals at the Gallagher Stadium.
Magnus Okuonghae's own-goal gave the visitors lead and then Louis Dennis wrapped up the points late on.
Bromley's win also brought to an end Maidstone's unbeaten home record.
"It was going to come to an end at some point," said Saunders. "It's disappointing, first-half we never got going - we looked like we were still on the way home from Barrow.
"Take nothing away from Bromley, they started the game very well and worked very hard.
"We grew into it in the second half and we put them under pressure but when you're really pushing for it you're liable to them nicking another goal and that happened.
"I don't have much luck against Bromley. I can't remember beating them since I've been manager, maybe they're my bogey side.
"We've been on a good run and we have to dust ourselves down and go again Saturday."