Finding covid’s spike protein in someone means that they currently have or are recovering from a covid infection. Finding covid’s spike protein in someone does not mean anything about their vaccination status.
So a recently vaxxed person that’s never had covid would not have any trace of a spike protein?
If that’s what you’re saying I’d love a source. The “friend” prolly won’t read it, but I’ll at least peruse it and file it away for the inevitable next time he drops this claim.