Alright, this happened twice while I was getting water buckets for a fishing pond, when suddenly I put the water down to catch my fall (Like 5 blocks) it didn't catch me and then the water just vanished. Then it happened again, I went to get another, came back to my camp and discovered when I put it down, Poof it's gone.

What I expected to happen was...:
I expected to pick up the water, run back and be able to put it back down, like normal.

What actually happened was...:
Then the water just vanishes as I put it down, and the first time I just thought I'd missed the water, after coming back with an empty bucket.

Quick side note: The original water block was still there. I tried it again, Poof again, and then one more time and it worked.

Steps to Reproduce:
1. Not entirely sure how to reproduce it, but I'd just look for a natural water source (Mine were underground, not sure if that helps.)
2. Then attempt to pick it up with a bucket in Survival.
3. Walk away, then try to put it down. For some reason it just vanishes.