We are not vets here, so it’s very difficult for us to say – as I’m hoping you understand. To me this sounds rather like an ear-infection. Possibly a middle-ear thing that then caused his ear-drum to rupture, which would have given him relief. Have you seen any goo in his ear? How does his ear smell if you put your nose there? There would’ve been no smell and bno goo when you were at the vet if it was a middle-ear infection. But such an infection is consistent with head tilt.
Panacur is often given against a common parasite that causes neurological problems. The treatment should be given for 28 consecutive days to eradicate the parasite.
Strokes in rabbits are rather rare and your bunny is young, but ear-infections are common and should be treated with antibiotics. The commonest kind prescribed for ears is Baytril. Did your vet prescribe any Baytril?
If it was a stroke, it will have to heal on it’s own, just make sure he eats and drinks and poops.