Does he seem alert?
Have you got painkillers for him?
I have no rabbit experience but my young guinea-pig boar was castrated in July (he weighs 3lb so probably the same size as your mini-lop)
We were asked to bring a water bottle and a tub of his favourite snacks for after surgery.He doesn't drink (ever) so along with the bottle I took cucumber,peppers,red topped cos, parsley, watermelon.
We put him in his Pighouse (he had two females in quarentine accomodation) so we thought he'd like to chat but this was the height of summer.
We put hay in loo roll tubes and gave him white towels and a cream fleece to sleep on (to spot any leakage)
He'd had a painkiller injection so we had three days worth of liquid medicine + a syringe to administer and he scoffed it down 
Keep an eye on the rabbits droppings, if you give him some of his favourite treats he'll appreciate them. Dandelion leaves? Grass? (Fresh hand scissor cut
)
He'll be a bit meh but they wouldn't have released him if he wasn't safe to go home.
Good Luck. 