Stack had not saved a spot kick all season but dramatically kept out Joel Grant's last-minute effort to ensure Barnet won their last-ever match at Underhill 1-0 against Wycombe.
"My heart sank," he said. "It's not an ideal scenario. We were 1-0 up and I hadn't had much to do for the entire game.
"We like to throw up surprises but I was gutted when he pointed to the spot. However, I am a confident goalkeeper and I believe on my day I am capable of saving anyone's penalty.
"Before I came to Barnet I had a good penalty-saving record but I have faced 11 penalties this season and that is the first one I have saved.
"It was disappointing earlier in the season, but I did always say I would save an important one!"