I accepted your answer. But in fact in our case it was a bit more complicated. We removed this issue from the active sprint, because of some misunderstanding. Then it was put in status Done and moved back when sprint was still active. And now JIRA report shows is as completed outside of the sprint.
I have an issue with this as well. Issues completed outside of sprint are showing up in my gray commitment bar chart on the velocity chart. This is creating inflated commitments for some of my teams. It seems that if someone finishes a story in a 'future sprint' before that sprint starts, the story is counted as a commitment in the velocity chart. I don't think this should be the case. Is this an known issue? Is there a workaround to it?