Oh I am so sorry. It is very hard to lose them and see them pass away. I know that is a difficult thing to process. But in hindsight, if we had a choice, wouldn’t we always choose to be holding them, that they be with the ones who loved them the best when they go?
My feeling is that it wouldn’t have been to do with the bite on the ear. For what that is worth…
It appears something came on very quickly. It could be a variety of things. As Azerane mentioned, GI stasis is common. It can also occur alongside other conditions. For example, if a rabbit had severe pain from something like a kidney stone, they may stop eating and then their gut shut down.
Bloat is another condition that can come on very quickly and often take a rabbit.
There are also things like undiagnosed heart condition, liver lobe torsion or simply a bite from a poisonous insect . There is also rabbit calici virus in some regions of the world that can take a rabbit very quickly. 24 hours after infection and often without visible symptoms.
To truly determine the cause, a necrospy would have to be performed.
I would have done exactly as you did. Made vet appointment and held them to try get them warm and comfortable.
Again, Im sorry for your loss. Binky Free little Bun.