I saw a similar scenario at the Hambrick open back in July. The TD put all AM2s in 3-somes. Someone who was supposed to be on my card started one hole back. Since you cannot play a tournament round as a twosome, we had to try to find out what to do. The TD decided to have us wait until the other group finished the previous hole and then let him join us (the correct card) with no penalty. Then he would witness me and the other player on my card play our last hole since he already would have played it at the beginning. In this case, it was probably his fault since he set everyone up in 3-somes, which leaves you susceptible to this scenario.
If everyone goes to the player's meeting and checks the board before heading out to their holes, then this kind of thing doesn't happen. I know a lot of people at tournaments are trying to get an early look at the board so they don't have to fight the crowds after the player's meeting. I'd say it's worth it to make sure you get to where you need to be.
The leaderboard can change before the player's meeting for whatever reason. Someone might have to withdraw due to illness, injury, or some other emergency (You're not going to hear from the people who say "screw this, I'm going home" so I don't think you can really prepare for it). Maybe the TD decides to run 4somes instead of 5somes. The best way to ensure you go to the correct hole is to check that thing after the player's meeting.
Would it be worth it to go to the PDGA with this scenario to get some more insight and possibly a rule clarification?