His place in the team was put under doubt when Leicester defender Ben Thatcher was called into the squad. However the one time England Under 21 cap will miss out with FIFA refusing to ratify his change of nationality until 19 February.
Caretaker boss Graham Rodger requested that Barnard be allowed to travel back for the Bristol game and then return for the Scots game. That request was granted by Hughes.
Rodger paid tribute to the forerm Bayern Munich striker for his co-operation.
"I've spoken to Mark Hughes, who has done this club an absolutely massive favour," Rodger told BBC Radio Humberside.
"He says at this moment in time he's prepared to let Darren come back and play. I can't thank him enough. It's his right to keep the player there, he's got his own issues and has to prepare his own squad.
"I think he's had a look at our situation here and has agreed to allow 'Barney' to come back and play. He deserves a bottle of champagne and that's a fact."