The guy who released the player like a dumbass should be ecstatic that you'll entertain sending him back. Asking the commish to force a return — which he does not have the power to do anyway — adds arrogance and a lack of responsibility to being a dumbass. If you're not offered back a player who will improve your ML team, keep the guy you claimed. If I were the dumbass, you'd have two or three trade offers from me as soon as you said you're willing to reverse my mistake — a SUA or LRA type, a solid bench bat, a decent catcher who can hit or a great one who can't, a great (not mediocre, as in Blanco) all-glove middle infielder, etc. If I had little depth and needed all my useful ML players, the offer would be a good prospect — late 1st round, supplemental/early 2nd at worst. Not that I'd ask you to trade him back in the first place.
Half the owners who might complain about you keeping him would do the same, and wouldn't even think of trading him back. If all you are offered is a turd, agree that the commish should try to force a reversal and see how far it gets with support. If the owner has played more than 2 seasons, anyone who ridicules you for keeping him instead of ridiculing the dumbass is wrong. You would not be the one responsible for any firestorm.
There's always a chance it wasn't even a mistake. An owner with an alias holding a high waiver position might try to slip that team a stud without fear of a veto. If anyone other than the alias claims the guy, post that it was a mistake and ask to get the player back for free. If the alias gets him, post nothing. Not saying that's the case here, but if it were it wouldn't be a first.