Daniel Nardiello scored deep into stoppage time as Bury prevented Scunthorpe boss Russ Wilcox beginning his full-time reign with a win and the Iron moving joint top of League Two.
The visitors went ahead through leading scorer Sam Winnall, who finished a lovely move by tapping the ball in from close range.
Winnall was causing the home side problems all afternoon and thought he had won a penalty when he bundled his way through two challenges in the area, but was booked for diving- a decision the referee got spot on.
Scunthorpe went two ahead on 68 minutes when David Syers burst through and fired the ball across the box for Winnall who bundled home past Jensen. He raced over to the Iron fans behind the goal only to be sent off for his celebration, which was deemed overzealous by the referee.
Matt Godden replaced Deon Burton but with the Iron already down to ten the replacement striker suffered an injury. A strong tackle from Richard Hinds meant Godden had to limp his way through the last ten minutes.
The hosts pulled one back when Chris Sedgwick fired home from inside the box after a great save from Sam Slocombe.
The Iron defended well until the last kick off the game, when Mirfin misjudged a ball forward and Nardiello fired past Slocombe to snatch a share of the spoils.