I am unfamiliar with reference type “free text” but if that is a stand alone field in a style, and not in the authors, year, title - it will show up “blank” in the library view unless you choose to display the generic field that “free text” is assigned to (and then it would be a later column).
For the field to show up in the reference list, the bibliography template associated with the reference type would need to include that field. – also, depending on the citation style, if numbered, in order of appearance, it could work, but if you need (author, year) style - that won’t work either, athough you could generate it manually.
Is this just because you don’t think you will ever use this specific citation again? I think it is more trouble than it is worth to skip entering the record as needed into each field into your library.