But what if there is not random encounters? The last time I played and adventure with random encounters was probably around 2010. If the party is sleeping in the dungeon then presumably I can too. If the party is not then I am not either and I will meet up with them when I am back regardless.
It is not that hard unless someone wants to make it hard for the sake of being hard.
Player agency. If the player wants to leave, that is the player's choice. And if I am not playing next week I am DEFINITELY leaving.
I am not talking about shopping. For example, we are in the middle of investigating cult activity and we are going from place to place, picking up clues and interviewing witnesses and maybe searching some places. Why can't one of the PCs take the day off and go back to the inn?
Or the party can drop bread crumbs so you can find them like Hansel and Grettle did ... which any group is going to do if someone misses a session and the DM starts pushing this BS.
Since this is a game with rules, it is relevant to look at what the rules actually say on this. The first two exerps from the DMG on what to do if a player missies a session:
"Fading into the Background. Have the character simply fade into the background. This requires everyone to step out of the game world a bit and suspend disbelief, but it might be the easiest solution. Act as if the character were absent, but don’t try to come up with any in-game explanation. Monsters don’t attack the character, who returns the favor. On returning, the player resumes playing as if the absence never happened.
Narrative Contrivance. Decide the character is elsewhere while the rest of the party continues the adventure. Come up with in-game reasons for the character to temporarily leave the party and rejoin later, such as following up on a rumor or reporting back to the party’s patron."
So aside from the fact that we do this at every table I play, the rules actually tell us to do it. Nowhere do the rules say you should kill off a character if a player misses a session.
So at the end of the day, yes we decide the character is elsewhere and that is RAW!