1. The most common scenario:
A vanity handicap (which the USGA estimates outnumber the sandbaggers by about 3 to 1) plays poorly in a competition when faced with stroke and distance penalties, putting everything, playing the ball down, etc., and loses to a higher handicap player whose handicap is higher precisely because he obsessively plays by the Rules and counts every stroke he possibly can. In the grill afterwards, the low capper bitches that he got sandbagged, which he did; BY HIS OWN INDEX!
2. The second most common scenario:
Both players are accurately handicapped, but the very consistent lower handicap player has an "average" day and shoots about 3 shots above his index. Meanwhile, the higher handicapper has his "once in five rounds" where he shoots below his index. In the grill afterwards, same conversation.
3. The third most common scenario:
The high handicapper, who we'll say is a 12, wins the match or net division or whatever by shooting a 79, and lower handicap players grouse to each other that "He's a 12, and he broke 80!", not realizing that the course rating from the tees they played was only 67.3, and the the high handicapper simply played to his index that particular day.
4. The fourth most common scenario:
The high handicapper is a sandbagging douche.
1, 2, and 3 all happen a LOT more than 4, but low handicappers believe that it's 4 every single time. It happens, but it happens a lot less than most believe.