Some sand bug I guess..?

Non-Moving, Uncollided Sand..?
I didn't know how it happened, I was trying to debug and when I exploded a buncha TNT there was this..weird sand block?
What actually happened was.. It wasn't suppose to happen and theirs a chance. It appeared about a minute later, I could walk through it and it made me black. It was some weird sand block.

Steps to Reproduce:
1. It doesn't happen all the time..but I think when I did THIS it happened.
2. When I exploded a large amount of TNT, I picked up alotta sandstone and sand.
3. Its a chance to happen, but during it I saw a floating sand block misplaced. I couldn't break it and I could walk through it.
(got a minecraft screenshot)