To your point, yes, you could trace back through Windchill and see what happened, but you'd be putting yourself in a more complicated situation than necessary.
Here's a simple scenario to consider:
- User wants to "delete" a file. You renumber it, and hide it from view
- Now the original number is available again, so you assign it to a new design
- Someone else now needs to recover the "deleted" design
What would you do here? Assign a new number to the original design? Change the number on the new design, so you can use the original number for the original design? What if the new design has already gone to production? You could try to write rules and policies for all these scenarios.. or just make one rule that numbers can't be reused, period. To me this is the cleaner solution.
I can relate to users wanting to delete files. I try to not allow it as much as possible. Obsoleting the file is better. The only case where I feel it's justified to delete a file is when the file existing creates confusion. If it's just old data that will no longer be used, just obsolete it. You can even move it to an obsolete folder so it doesn't clutter up the folder structure.