When I threw my trident towards unloaded chunks (during a rainstorm, in the positive x, positive z direction), it started floating in the air as if it has hit something. Once the chunks loaded it was still floating there, even though it was not touching any blocks. It was enchanted with loyalty III, mending I, unbreaking III, channeling I, and impaling V, although I'm not sure if that affected it, except that it should return to me. I tried towering up to where it was to pick it up, but it did not change when I walked back and forth through it. I tried putting blocks on and around it, but that did not help. I tried getting other players to walk into it to see if it would hit them. I tried going far away from it and then coming back. It was not floating on a chunk boundary. I have found no way to retrieve it, but it is still floating there.

Update:

I have tested some, but I haven't figured exactly what circumstances caused this. I don't have a way to reproduce my issue again. It seems to be relatively rare. I tried with lag, motion, and all the enchantments in survival, and that didn't cause it. I'd be interested and would be willing to do more testing if anyone finds a way to replicate this, but for now I don't think I can help (with steps to reproduce, etc).