This happened to me too. I was riding a donkey, and then I got off and they disappeared. I had ridden the donkey through a glitched group of chunks, where a large group of chunks has collision, but they are invisible and entities inside them act weird. This might have something to do with it. I don't know.
See, this confused me: Changing the enchantment levels offered by adding, removing, or blocking bookshelves alters the enchantments shown, but does not change possible enchantments; using another enchanting table with the previous bookshelf number still shows the previous enchantments. The enchantments for a particular enchantment level (with the same seed and item) do also differ depending on which row they appear in, but they are not "better" or "worse" based on the row despite the different resource costs.
Strange. I didn’t see that on the wiki, and I feel like it has worked differently before.
Ok, thanks.