So I've been having issues with boats disappearing the moment you get out of them, however they are still technically in the same place. This happens nearly ever time and has caused issues for me. As it seems the only way to get the boat is to walk a few chunks away, wait a few seconds and come back, and it should be wherever it was left. However I recently caught a video of what happens to it when it disappears. And just a warning before the video: photosensitive seizure warning.

https://youtu.be/RLw6saCEAlU