When running an Interactive Classifier job, the "File exists" label for the output files (such as the training data) reads as "False" until the IC job is finalized. However, it's possible to rename those files anyway. Once the file is renamed, it appears as one of the available resources in the input port.
An example with a training data file. The file is renamed, but doesn't exist:

And yet it appears in the available files for the training data input port:

If one mistakenly selects that file as the input resource, the workflow won't run and it won't be clear why.

Also, deleting the workflow run doesn't make the nonexistent file go away. And it's impossible to delete the file itself, since it doesn't exist in the first place!

I imagine a possible solution would be to ensure that even if a file is renamed, it doesn't become an available resource until the workflow run is finalized.