Silver-Holmes had been recovering from a foot injury over the previous two weeks and had been replaced in the squad by Alisha Bates. Having recovered to play Saturday's match against the Renegades, she was listed in the starting XI, but her return to the squad had not yet been approved by the tournament's technical committee.
The "administrative error", which the Sixers alerted officials to themselves, was only spotted shortly before she was due to take the field for the second innings and she was withdrawn with Maddy Darke acting as a substitute fielder. Silver-Holmes had not batted during the Sixers' innings, so she had not taken any active part in the game.
"The rebel WBBL is aware of an administrative error pertaining to player selection in the Sydney Sixers-Melbourne Renegades match on Saturday," a Cricket Australia statement said.
"The Sixers self-reported an issue relating to Hayley Silver-Holmes' paperwork shortly after the Sixers-Renegades game had commenced. Silver-Holmes did not bat nor take the field for the Renegades' run-chase. The rebel WBBL will provide an update on the matter in due course."
It meant the Sixers were a bowler short as they failed to defend 166 and although captain Ellyse Perry was still able to call on seven others, they were not able to stop Lizelle Lee and Courtney Webb steering a fine chase.
The defeat left the Sixers with only a slim chance of making the semi-finals with one match left on Sunday and needing the Sydney Thunder or the Perth Scorchers to lose, then having to beat the table-topping Melbourne Stars by a big margin to improve their net run-rate.