John Sutton hit the post for the visitors in the first half, while home goalkeeper Jamie Langfield pulled off excellent saves to deny Sutton, Jamie Walker and Michael Ngoo.
Locke was reasonably satisfied with his side's performance and work rate, but he admitted he is concerned over their failure to convert opportunities.
"That was one of the positive things for us, we are creating chances, but we can't keep missing them," Locke said.
"That is the story of the season for us, the chances we are getting we are not putting the ball in the net.
"That's probably the difference between the teams, Aberdeen got two chances and scored."