Both Walker and Warnock were keen to extend the arrangement but Spurs blocked any further deal.
"He helped us enormously during his time here," Warnock told the club's official website.
"We were keen to extend his stay, but they were against it. Maybe I'm being selfish, but I've got my own reservations about Tottenham recalling him.
"I think he'd be better staying here and getting another 20-odd games under his belt and learning some different aspects of the game, but they've got other ideas.
"Having said that, I'm pleased we've been able to play a part in Kyle's development and I wish him well for the future."