UI panel disappeared

Hi, i havent simple UI elements like buttons and text in my scene hierarchy. Only UI Toolkit
My version is 2022.3.11f1

You probably need to import the UI package into your project. You can do this by going into Window > Package Manager > Select the dropdown where it says In project to Unity Registry > then search for Unity UI and install the package.

Oh no . In my opinion, yours unity source is damaged or another settings are changed .