Invisible Chunks

My relative and I were playing Minecraft: Bedrock Edition in a survival world with achievements when she reports that she died in void and the message "[name] has fallen out of the world".  She told me that it was in an unspawned chunk on a mountain and after that it fell into the void and died, losing its items. Unfortunately, I didn't remember to take a screenshot of the death message. When she was reborn, she was reborn into an "invisible chunk".