This is kind of hard to recreate, as the bug was not able to be screenshotted and I was not recording. I'll do my best:

so I was walking through some trees in Minecraft 1.14.4 while getting home. I had a water bucket to nullify any fall damage I might take, but then, I jumped down from a high oak tree (maybe about 7-10 blocks higher than the top of the next tree I jumped to). I used the water bucket, but the water mysteriously disappeared right as soon as I put it down. My fall damage was nullified, but the water was gone. I did also repick the water back up almost immediately after placing it, but I guess the game thought the water was still out of the bucket while collected at the same time, idk.

TL;DR: i used a water bucket and picked it back up immediately after landing in it but the water was gone, and the bucket was not filled.