Why do I get "Ignored Assignment" warnings in the Fitter report?

I have a number of pins that are listed under Ignored Assignments that were once in my design and now are removed. I have no reference to them in the top HDL, there are no Location assignments to these pins in the Assignment Editor, and nothing in the QSF referring to these pins.

How do I find where these location assignments are coming from?

I am running Prime Lite 18.1.0 on Win10.

Thanks, John.