Lost world

I have a premium minecraft account and I use the official launcher. On several occasions, servers or worlds have been deleted from the launcher list. Since I play most of the time on online servers. I have no problem retrieving IP addresses and I keep playing without problems. For 8 months I was playing solo on my pc and I had created a survival world with many things and a lot of work time, but today I was playing and I began to notice that my pc was somewhat slow so I normally closed the minecraft session, restart my pc and I entered the game again. But my world had disappeared! It was not on the list.
Check the files in% appdata% and the folders with the name of my world was there but I don't know why it was deleted from the launcher list.
I would like you to tell me how I can prevent this from happening again. What am I doing wrong or what advice can you give me? This would not be a problem if the servers were from the internet because I could retrieve IP addresses, but it is not the same when the created world is on my own PC.
I already started a new world also in solitary survival and I would not like to lose it.
Here are some images with which I want to help you understand my problem and to give me some recommendation:
In the file "img1.png" is the initial screen of the launcher that I use.
In the file "img2.png" you can see the version of the launcher.
In the file "img3.png" I indicate the option that I use as solitaire.
In the file "img4.png" you can see that the list of worlds is empty.
Thank you very much for your time.