Should I cite an article that I can't find?
I would definitely try contacting your librarian at your university library. University libraries collect physical copies of papers and they might have this one. Librarians are also a lot more versed in navigating the various search systems and they will probably be able to find this paper, if only as a hard copy. It is also possible that your university does not have the paper, but they could contact different universities to get it.

I would definitely recommend to no cite what you haven't read, especially if you don't even know the title of the paper.

Edit: As others have also noted, it might be good practice in your field to in fact cite the paper, but with the caveat that you cannot find it, as suggested by Thredolsen's answer. If this is common in your field please do this.