In his first game in charge of the Tynecastle outfit the former Jambos skipper is forced to look on as his side throw away the lead and the Scottish League Cup at Hampden Park
After an early Ryan Stevenson strike saw the Tynecastle men take the lead, efforts either side of the break from Esmael Goncalves and Stephen Thompson helped the Paisley side towards lifting the trophy for the first time.
"I thought we looked the more likely to get the second goal rather than St Mirren equalising," Locke told reporters. "It was a poor goal defensively from our point of view and the start of the second half was the turning point of the game, we didn’t get started.
"Full credit to the players, they never gave up and that's the type of commitment and desire that's required at the football club and I can't fault the players in terms of effort.
"I was disappointed in the first 10 minutes of the second half, because we didn't get going at all and that's cost us.
"There's always defining moments in games and if [John] Sutton scores with the header then it would have been a different outcome, but it's all ifs and buts and we never took our chances on the day and St Mirren took theirs."
Locke also admitted that if his players had shown a bit more composure in the closing minutes, they could have sent the game into extra-time.
"We put a lot of balls into the box, but I think with Ryan Stevenson he's got that wee bit of composure and he showed that with the two goals he scored," Locke added.
"But when it's getting to that stage, we're just getting bodies into the box and you're just hoping it drops to one of our boys and unfortunately it never [did]."