Warnock was left behind when the 18-man squad jetted out to Germany to complete their pre-season preparations for their draw with Werder Bremen.
"I decided to go with that squad there that came over, and that's all there is to it," said Lambert.
"There's no update on Stephen Warnock or anything like that.
"It's just that that's the squad I chose to bring and that's all that I'll talk about it really.
"He's done really really fine, but those were the ones I decided to bring."