It has become somewhat common for a few players in our "club without real estate" to not turn in their score cards at the end of competitions or to quit the tournament round with a few holes to go. A few don't sign their own cards in order to be DQ'd rather than have their score listed in the results. I have never asked them why but presumably they are not happy with their performance and don't want their poor showing to be public knowledge. Of course, the rest of us aren't really fooled when these guys routinely have DNF, NC or DQ next to their name.
I was curious how the handicap system treated these situations. According to the USGA Handicap Manual, scores when one is DQ'd for not signing a card or not returning a card are still acceptable for handicap posting. If one stalks off the course in mid-round, the incomplete round should be recorded as either a 9-hole score (if 7 to 12 holes are played) or 18-hole score (if 13 or more holes are completed) using the "Holes Not Played" procedure. If you are DQ'd for using non-conforming equipment or some other reason that might be reflected in your score, the score is tossed.
This info will probably not be shared with the players who are guilty of attempting to hide their poor play. If they want to toss out their poor scores, I say have at it. More vanity handicappers in our competitions means fewer players to beat.