Hello, unfortunately I cannot give more specific steps than I've already given because the user who got this error was a child. He opened Blender, File -> New -> Sculpting (which starts from subdivided sphere) and worked for some time using Draw brush, most likely with Dyntopo enabled, and maybe Smooth brush also. X mirror option probably was enabled. No mode except for sculpting was used. There are no 3rd-party add-ons. And tweaks that I do to Blender configuration, if you need them, are:

Preferences->Viewport->Object Info=false; Preferences->Viewport->View Name=false; Preferences->Editing->3D Cursor->Cursor Surface Project=false; Preferences->Add-ons->LoopTools=true; Preferences->Add-ons->Rigify=true; Preferences->Navigation->Auto Perspective=false;