It was impressive that he was able to recover to save par.
His initial misfortune was shared with his playing companion, Padraig Harrington. The pair occupied the same fairway bunker at the 18th before the Irishman thinned his shot right over the flag and 12 rows into the grandstand, with the ball striking a female spectator on the right elbow in the process. Gallacher fared little better moments later - thinning his wedge shot some six rows back.
Both were afforded "free" drops and Gallacher saved par to record his best round at Crans-sur-Sierre with a score of 65 and finish the day tied on 10-under par, alongside Dane Thomas Bjorn, the 2011 champion.
"I guess if there was no grandstand I would have been out-of-bounds for sure, so I made the most it," said Harrington, who chipped in to also card a 65. "The woman was pleased to get a signed ball and I was pretty delighted to get the drop, and I didn't kill anybody, so that's not so bad."
Gallacher's round of seven birdies and just one bogey was his best by a shot in 24 rounds of the Swiss Alpine course. Victory here would complete the Omega double since he won in the Omega Dubai Desert Classic earlier this year.
"I'm putting well this week," said Gallacher, who is comfortable that he has overcome a back problem . "I am hitting the ball not bad - it was pretty ropey the last few holes, including that shot at the last, but overall not too bad. I'm in first place. I'm happy with that. It gives me something to work on over the weekend."
Harrington - who is tied for 13th - will also be content that he has not had too many mountains to climb so far given he is competing in the Alps for the first time since 2000. He found that playing alongside Gallacher made his return that much better.
"We talked about things such as the Walker Cup starting tomorrow in the States, players who we played against in our amateur days, so we always have a good time when we get paired together," said the Irishman. "Steve would have been a competitor of mine growing up and over time your former competitors become very much your friends."
In contrast, Richie Ramsay crashed out of his title defence after scores of 73 and 71. However, he was given some comfort around two hours after his round when the Scot unveiled his Former Champions plaque which has been set into the pavement on a Walk of Fame on both sides of the main street of Crans Montana. "This has given me great incentive to work hard next week's event in Holland," said Ramsay.
There were contrasting fortunes for three of his compatriots too, with Craig Lee just four strokes off the pace following a round of 65. He is two shots ahead of Paul Lawrie, who scored 70, although Glaswegian Chris Doak has been forced out of his inaugural visit to the competition with a foot injury. He was lying 10-over par.