Recovering file from the Visual Studio document cache?

Sorted it. Those recovery files are located @ MyDocuments\Visual Studio X\Backup Files\Project Name...

If you have compiled the code into a DLL, then you can use ILSpy, or Reflector to decompile that back into code.

Visual Studio 2019.4.1 had my backup files in %localappdata%\Microsoft\VisualStudio\BackupFiles - the folders in the MyDocuments tree were empty.