"Err... Well. I never really tried waking anyone under this?" Papyrus looks to Carly, because she'd been involved with it more times than anyone but Sans.

"I only really put people to sleep as... a Harbinger? And, uh, later tried making people happy. The happy part wore off on its own, I don't know if sleeping people... woke up."

He gives his brother a tentative shake, but looks worried all the while. Anyone who ventured around Wismuth after Harbinger Papyrus had done his thing may have run into his victims, and people even under the intense dust could be woken - with shaking and emotional pleas. This half-powered, creation dust variety, should take a lot less than that.