Did y’all sign their card for a 69? If so, you shouldn’t have brought it to anybody’s attention, because that’s on y’all unfortunately. I’d have taken it to them (people who I suspect cheated and the scoring officials) right after walking off 18 and counting it up.
But...
It was your buddy, at his club, and you gave him the option. I guess he didn’t want to do anything about it, which is understandable (club event/reputation).
What would I do? Exact situation, me being you? Probably the same thing, ask if he wanted to say something. If he didn’t want to say anything, I’d just keep my cool. If he wanted to absolutely say something and pursue a DQ for them, I’d be with it. I also don’t know what the seriousness of the event is. I mean, people should never cheat under any circumstance though 🤷♂️