[The silence catches his attention, and that expression... It's hard to pin down, but something's not right. More than Sans's explanation, after, accounts for.]

Oh, is... that what it is. [Papyrus can't find it in him to believe that - but he can't find it in him to challenge the answer, either. More lightly, he offers:]

Well, we can't all be master planners. If I get an idea, I'll let you know! Keep your phone on.