Fishers police say no one was injured from the gunshot about 2 p.m. Monday at the furniture store along Interstate 69 just northeast of Indianapolis.
Police Sgt. Tom Weger says the handgun's owner wasn't aware the weapon dropped from his pants when he sat on the sofa. The child later found the gun in the sofa cushions.
The child's age wasn't released.
Weger says no arrests were immediately made and that the Hamilton County prosecutor's office would decide whether to file any criminal charges.
Ikea said in a statement it has a no-weapons policy for its stores and that it was cooperating with police.
RELATED: FBI agent's gun accidentally discharges while dancing in nightclub