Turnbull and his team-mates crashed to an embarrassing 10-7 defeat to rugby minnows Spain in the Bowl semi-final of the HSBC Sevens World Series event yesterday.
"It was hugely disappointing," the winger admitted. "We got off to a good start yesterday by beating Kenya in our quarter-final. It was good to put them away. So losing to Spain was sore. I thought Spain were a class outfit. We gave them the ball for the majority of the game.
"But there are positives to take from the weekend. We were beaten narrowly by Wales and South Africa, teams which made the Cup quarter-finals, on the first day. If we had enjoyed a bit of luck in those games we could have been up in the top tier."
With a total of 26,494 fans attending over the two days, Turnbull was impressed with the new venue for the international tournament at the Scotstoun Stadium.
Despite Graham Shiel's team crashing out yesterday, he remains confident the national side will perform better when the Sevens event is staged at Ibrox in the Commonwealth Games in two years' time.
"The event has been excellent," enthused Turnbull. "I was amazed at what the organisers did with the stands. It brought the atmosphere right on to the pitch.
"One of the reasons for bringing the tournament here was because we are going to be in Glasgow for the 2014 Commonwealth Games. If we can get a crowd like we had this weekend it will be fantastic."
New Zealand consolidated their position at the top of the HSBC Sevens World Series ahead of the final round this coming weekend with a 29-14 victory over England in the Cup final.
Elsewhere, Samoa lifted the Plate, Russia the Bowl and Kenya the Shield after final wins over Wales, Spain and the United States respectively.