Quick question on earned runs--

In a launch league game this week, my closing reliever gave up one hit and an unearned run for the loss. My team had no errors, balks, passed balls or wild pitches. How else can the run be unearned? I'd know the answer but it was an away game.

It may be a statistical glitch -- my opponent also earned 4 RBI, but only scored 3 runs.

For reference, see LL11, Pixies at Norsemen, game 2.