No, never experienced this. Upon creation of a new app, this app gets stored on a drive local to your computer. So try again to create an app and then find that location by Following Mx Studio Pro’s menu ‘Project’->’Show project in directory explorer’.

Also, if during creation of the app you select

then Mendix will have and maintain a copy on their server too.

Best of luck.

I can find my app on my computer (Mx Studio Pro’s menu ‘Project’->’Show project in directory explorer’), but there is nothing on the mendix platform.

Above is the screenshot when I open mendix platform, the "Test" app is created after all other apps were gone

Above is the screenshot of "My app" when I open the mendix pro

I don't really understand why...

What happens when you try to update the application? 

If the projects are deleted/gone, this should give you an error. If it updates, then you might be logged in into a different account in the Mendix Cloud.

It can happen if you didn’t commit your changes, and then accidentally deleted mendix project folder.

Perharps, you could also had missclicked the “Revert All Changes” button on Version Control maybe?

Are you working alone or with more people in the project? Maybe someone could commit removing things you created…

Thank you for all your help, all my apps are back today, I didn't do anything about it, I think it's just a system error or something.