The Crystal Palace boss wants to send the Austrian back as he has failed to break into the Championship side.
But Warnock hasn't been able to contact anyone at Anfield - and has now threatened to send a pigeon.
"The deal is until the end of the season - but it is pointless him being here because he isn't going to play for us," Warnock told the Croydon Guardian.
"I have asked them to take him back so he can go elsewhere. I am sure three or four clubs will have him, so it seems silly that he stays here.
"Nobody is returning our calls - it is ludicrous. They must really care about the player. We might send a pigeon up next."