the same thing has happened to me, its normal because chess.com will automatically put you in vacation mode if you are about to run out of time in your games. So even though the player might not be on vacation, they will still be put in vacation mode.
Vacation question
If you need help, please contact our Help and Support team.
Is it weird that one of my opponents is on vacation and yet I have seen him logged it twice and once he was playing live chess?