Somebody stayed awake past midnight on the couch pretending to watch TV until they heard your key in the door.

Some care is deliberately disguised so it does not become an obligation. Nobody says they waited up; they say they were watching something and lost track of time. The pretending is part of the gift, because being told you were worried about would have made you feel followed. You were being looked after by someone who did not want it to weigh on you.

If this happens in your house, say you know. Not as an accusation, just plainly. And text when you are on the way home, because it costs you nothing and it ends the waiting.