I discovered this as well. It appears to only happen to me if my inventory is otherwise full at the time that I try to use the full or empty bucket. If I have at least one empty slot at the time that I use the bucket, everything works normally.
EDIT: This was using the Amazon.com build on a Samsung Galaxy S III.
It is definitely still an issue. I lost several buckets before I figured out how to avoid the bug. As a computer programmer, I know the value of specifics when it comes to finding and fixing bugs, so I was trying to help the Minecraft developers isolate the issue as quickly as possible.