Andy Keogh's second-half strike proved the difference after Will Hughes cancelled out Liam Feeney's opener and the Lions are now unbeaten in nine matches.
Jackett missed the match with flu but assistant manager Gallen said he had sent in his instructions from his sick bed.
"Kenny has just got a bit of flu and he'll be back next week," said Gallen. "I had an idea on Thursday he wasn't going to make it but carried on with what he was going to do.
"Kenny picked the team and discussed what training we are going to do and told me what the team needed to do. He was here, but not here.
"The team has been defending and running and working and blocking for the previous nine games. It's been a big feature of our performances.
"(With) the disappointment of an equaliser after half-time, it took us 10 minutes to compose ourselves and we did well to nick a tight game."