They are out. A choice that sat on their desk is now on yours. The two failures are mirrors. You wait, and they return to a pile that grew in the dark. You decide, and they return to a world that moved for reasons nobody wrote down.
A handoff is what you wished they had left you. In a small way, you now write that document backward — after the decision, for the person who could not be there.
Decide only what cannot wait
If they said "this waits," it waits. If you would undo the choice the morning they return, it is not a decision; it is fidgeting. Everything else is fair game, and delaying it so you can feel polite is how leave becomes a second job.
Ask for the decision from whoever actually owns it now — you, a deputy, a skip-level. Close the list. Write the recommendation you are about to take. Then take it.
Write the reason as if they will disagree
Two sentences. What you chose, and what made the alternative worse. The second sentence is the one they need. It tells them whether the decision is still right on the facts they have in their head.
State the assumptions you used. "I assumed the vendor window on the 20th was real because of the email on the 3rd." If they know that email was superseded, they can reopen one line instead of the week.
List what you did not touch. "I did not change the pricing page. I did not write to the customer." Absence of a change is invisible unless you name it. They will otherwise assume you changed everything.
Send the record to them, and to whoever is covering
A briefing to the person on leave will wait. That is fine. It is a letter for the first morning back, not a page they must open on a mountain. Copy the covering person as their own thread if they need to act — RelayLink threads are two people, so do not try to cc. Send once to each, or write one brief and send it twice.
If they have an account, you need an accepted contact. If they do not, they get email and a page. You approve the words. There are no attachments; link the tickets.
Use their name. A private nickname does not belong on a record they will read when they are tired.
If you already talked the choice through with an assistant, connect it and have it write the reason while you still remember why the other option lost.