This is a follow-up to "why-didnt-they-ask-aharon-to-lead".
In Parshas Yisro and later we learn that the Jewish People had some kind of "the chain of command" or at least "the chain of judgment": Moses, Aharon, Aharon's sons, the 70 elders, the other judges appointed after Yisro (that was after Yom Kippur but anyway) and the rest of us.
When G-d invited Moses to come up the mountain it was seemingly dangerous, with a good chance of not coming back (why not? the angels wanted to hurt him, G-d was furious sometimes, the weather was bad - fire and smoke, he didn't eat etc).
We all know that every country has a clear protocol defining the chain of command and the order of actions/responsibilities in the case of certain incapabilities of the leader(s) (is it the 25th amendment?).
I would expect Moses to leave clear instructions for such a case: "Eyes on me everybody! If I'm not back on the 17 of Tamus and you don't hear anything from me I herein appoint Aharon to be my replacement. If Aharon somehow is not available his sons ... " etc.
So, was there a clear "chain of command" in the Jewish nation and if (apparently) not, why didn't Moses care for that?