How to distinguish between unsaved drawings via API?

I'm currently building an add-in that creates drawings. When switching between models, the task pane switches to show the appropriate controls for parts/assemblies/drawings. I'm now looking for a way to distinguish between multiple unsaved drawing files. Is there a proper, robust way to do that?

Persistent IDs sounded great, but those are only attached to features and entities. I did find this forum topic about file IDs, where it is told that we cannot access the internal file ID. Comparing creation dates would be the best solution.

My problem is that the drawing files are still unsaved. At least by the user. Is there maybe a temp file created somewhere?

SolidworksApi macros