[ Even if Luffy has no advice... simply being told "my brother got lagged behind" helps. Like, a lot. It means he's not the only one this happened to! That there are multiple brothers, being separated by one of them being too lazy to keep up!! Seriously, that helps. ]

I think that is what happened as well! Surely, he just must be left behind somewhere in Oska, and I will see him later!

[ except, that's not really what happened. ]

You've met skeletons before?? Ah- wait! I have heard about this from... someone.

[ He doesn't remember his name. Whoops. ]

...Anyway, my name is the Great Papyrus!! It is nice to meet you, human!