Johnson had looked to extend the 31-year-old's stay at Ashton Gate following his final appearance in Saturday's defeat to Reading but after talks between the club, it was decided the player would return to Molineux.
Johnson has also been linked with a loan move for Wolves striker Stefan Maierhofer but whether something happens in time remains to be seen.
That means Danny Haynes - who replaced Iwelumo as a 46th-minute substitute on Saturday - could come into the starting XI while John Akinde is also staking a claim.
Defender Liam Fontaine was brought off as a precaution after he picked up a knock, although he should continue despite Jamie McAllister's return to fitness.
Evander Sno, Jamie McCombe and Marvin Elliot remain long-term absentees.