Stone and Dirt Wall

I was building in a flat world, then I saw a stone and dirt wall. My siblings were playing too, yet they couldn't see the wall. I tried to break it. So, I punched it. The block I broke was broken, but as well as the block above it. The wall now pops up in my worlds. If you leave and rejoin, the wall disappears. Oh by the way, I my first encounter was in Bedrock Creative mode.