I was working on an entirely survival world on my phone and ventured to gather clay in a nearby river. I then saved and exited my game while still in the river. About 5 minutes I reopened the game and entered the very same world. However, I found myself very very high in the sky only to land in an area that was entirely different from when I left. I then ventured to my last location in search of my items only to confirm that I hadn’t died in the same space that I left off at. I tried to recreate the event by going in water and saving and exiting but I came back in the same place normally.
Linked issues
duplicates
Comments

Thank you for your report!
However, this issue has been closed as a Duplicate of MCPE-38374.
Please add a vote and any new information to the main ticket, which will be updated accordingly.
If you have not, you might like to make use of the search feature before making a new ticket, as it's likely that the issue has been reported already.
Quick Links:📓 Issue Guidelines – 💬 Mojang Support – 📧 Suggestions – 📖 Minecraft Wiki
I have the same problem. I save properly and I turn back dead. (Windows 10 edition)