In my experience post cards can take forever to turn up, so if he had planned to send it while away (which seems likely), it seems possible that it just hasn't arrived yet. It's horrible waiting and worrying, especially when all the abandonment fears kick in, but try not to panic. Maybe it'll come in the next few days. If T is okay with contact and you don't get the card towards the end of the holiday, would it feel okay to send a quick text or email to check?