I traveled in the opposite direction (more or less: Vienna to Bucarest) more than 3 months ago and wasn't asked either, but on the Hungary-Romania border, they put me in a tiny room (1/3 shipping container or so) with ca. 10 people and gave me quarantine papers. They didn't check bags.

I'm pretty sure they'd check for a test or vaccination now on the way back, I'm not eager to find out and will stay here in the Covid exile for a little longer.