They switch the two species on the indoor and outdoor exhibits.
As of this year, it appears the rotation of the sun and sloth bears at Columbus has ended. All signage for the sun bears has been removed from both exhibits and I have not seen the species in any of my visits in 2018. Unfortunately, I have not yet been able to find anyone knowledgeable to ask what has become of the sun bears (for all I know, they may still be around off-exhibit, and were removed from the exhibit rotation when Columbus received their new female sloth bear from Germany).