In the screenshot, you can see the coordinate axes in the scene window where the character model should be. It was there, and everything was fine. But sometimes (I haven't figured out how to reproduce the error yet), the model disappears when selecting it in the scene hierarchy (specifically, in the scene hierarchy, not when clicking on the mesh in the visual scene window).

Restarting the editor doesn't help. The model remains invisible.

The visibility checkbox is active: