Frodo must have had many many conversations with the others. They'd told Bilbo a lot of the story in Rivendell, so he no doubt had the framework, but I can see him trying to elicit details from them. And *snags another bunny* you could also play it up in a parody where the hobbits are complaining about Tolkien taking the basic framework of the story and adding all sorts of emotional bits as he "translates".

I'm looking forward to seeing what you do with the bunnies.