Hi,
Usually, it should be in your saves folder in your Minecraft folder on your device. If you do not see it, check your backup folder and version folder, if any.
If you do not see any of them, please check the Microsoft account you use to see if it is signed in to the same account you usually log in with for that world.
If you log in with the same account, I recommend requesting support on Minecraft to help you further with your save World. It can be an in-game issue and not an MS account issue.
https://help.minecraft.net/hc/en-us/request/new
If you need additional assistance, please let me know.
Stay Safe!