Tommy Allan's penalty and Adam Ashe's converted try had pushed Lineen's side into a 10-3 advantage before Selponi's late intervention.
And after finishing this year's Championships with two wins from their five games, good enough for fourth overall, Lineen was left to ponder what might have been after narrow losses to both England and France.
"I'm very proud of the players, they came close and performed very well. France at the end looked like they had won the World Cup and I think that showed how hard the players worked," he said.
"We will take a lot away from this game again, but a few basic errors cost us. It is important that we learn to win these games."