Two tries from George Horne and one each from Peter Horne and Matt Fagerson had Warriors 14 points clear after an hour, but two late tries and Scannell’s last-gasp penalty gave Munster the win.
A knee injury to Sam Johnston could have implications for Gregor Townsend’s Scotland squad for the autumn Tests, and Glasgow coach Dave Rennie admitted the centre had suffered a significant blow.
“Sam Johnson is a big question mark. He injured a knee tonight. We don’t know the extent of that but he didn’t look that flash,” said Rennie, who side were within seconds of a memorable bonus point win.
“It’s tough. There massive disappointment in the changing room, the boys are really down. But I’ve spoken to them, told them how proud I was.
“We were ten seconds from leaving with five points which would have been great but we fell short.”
Warriors leave with two bonus points but they were left crestfallen as Munster celebrated.
At times this was a game marred by late hits and off the ball antics. The needle was evident early on. Less than two minutes had elapsed with both sides were involved in a heated exchange of pushing, shoving and jersey ruffling and a couple of minutes later a second flashpoint drew a penalty for the home side.
James Cronin barrelled over with the help of John Ryan to give Munster the lead. Glasgow stand-off Peter Horne was then collared behind his own posts but CJ Stander could not control the ball at the back and Glasgow cleared their lines.
It was a similar story after 19 minutes when Munster’s ball control in attack let them down from a maul off an attacking lineout, and their inefficiency was punished 15 minutes from the interval when Warriors struck from deep.
A turnover ball found its way to Rob Harley and it was his long pass to the left that found Munster outnumbered. Quick hands from Rory Hughes and Peter Horne freed his younger brother George Horne and he showed great speed to beat Keith Earls to the corner flag.
Glasgow then took the lead when George Horne claimed his second try. Nick Grigg can claim the plaudits though as his smart line breached Munster’s defence and he picked out his scrum-half for the score, which was converted by brother Peter to give the visitors a 12-7 interval lead.
A heavy collision with Stafford McDowall resulted in Munster’s Sammy Arnold’s evening coming to an early finish just before the interval, and in a reshuffle Earls ended up in the centre for the home side.
Only a forward pass denied George Horne a try before the break, but Warriors came within inches of their third try six minutes into the second half. Quite how Peter O’Mahony got back to deny Ruaridh Jackson after suffering a brutal hit at the other end is a wonder, but the Lions flanker forced the knock-on, although Chris Cloete was sin binned for his off the ball tackle in the same play.
Camped on the Munster line it was just a matter of time before Warriors scored, though, and Matt Fagerson finally crossed off the back of a five-metre scrum.
The Glasgow dominance continued and they claimed the bonus point on the hour mark. With a penalty advantage to gamble with George Horne chipped over the top and Peter Horne did well to climb high and score.
There was a smart Alex Wootton finish 15 minutes from time to lift Munster hearts, and Mathewson also stretched well to score seven minutes from time before Scannell landed the winning score.