Refugee advocates in Australia want to know what has happened to Farhad Rahmati.
They say they are extremely concerned for the Iranian refugee's welfare after he was "disappeared" from the Brisbane Immigration Transit Accommodation detention centre on Thursday morning.
The refugee was removed from the gym by a number of guards and has not been seen since.
Mr Rahmati had previouswly highlighted the plight of the hundreds of people transferred from Manus and Nauru under the Medevac laws, but who are still being held in detention in Australia.
His forced removal from the Kangaroo Point hotel to the BITA camp in June this year began a series of protests.
The Refugee Action Coalition's Ian Rintoul says Border Force must reveal Mr Rahmati's whereabouts.