I haven't exactly had this scenario come up yet, but it has come close and I just wanted to get other opinions on how to handle it.

Players are in a Draft at Regular and 2 players completed their match fairly quickly. They decide there is enough time left in the round to go eat and leave the venue. Everyone else in the draft finishes with 5 minutes left in the round. My understanding is to go ahead and turn over the round and the players who left to get food have however much time was left in the previous round to show up before we start counting down the 10 minutes to a match loss. If they show up before 10 + (time remaining in previous round), give them an extension and remind them to try to get back earlier next time.

However, if the round ends 12 minutes early and we turn the round over, I'm not sure if I would only give them the 12 minutes into the next round before I drop them. Asking their opponent to wait 22 minutes into the round before giving them the win is quite a lot, and a 22 minute time extension could make other players upset if they have to wait for the next round.

A player isn't considered tardy until after the time the previous round should have ended. So they are tardy at 12 minutes if the next round started when the previous round would have still had 12 minutes in it, and they won't be dropped for No Show until 10 minutes after that.

So there is an alternative to having one player sit and wait for 22
minutes. You can have everyone wait for 12 minutes before starting the
round, then that player will have some company while he's not playing
Magic. Then he's only going to be not playing alone for 10 minutes.

I'd explain the player without an opponent that X en Y aren't going to be
considered tardy until 22 minutes from now, but he could try and save
everyone some time by spending up to 12 minutes to find them. Considering
it's REL, it's not going to be a top 8 for something important, so in that
case I'd ask the opponent if he would be okay with me asking if anyone
knows where X and Y went or have their phonenumber, so X and Y can be
informed the round had started earlier.