The boy - referred to as "Jack" - was released on probation last week after 60 days in custody at Cleveland Youth Detention Centre in Townsville.
He is understood to have spent 22 consecutive days in isolation.
Queensland's human rights chief says the case may have broken state laws.
"If he's being locked in because there's staff shortages, and Cleveland detention centre has 80 or more kids in at any one time, one can only assume that other kids are in the same circumstance.
"You would hope not, but maybe it's more common than we thought."
