Screw vanishing cars, I've got the worst bug you could imagine. I'm 58% through the game, with ~37 hours on the clock and my game is broken. No missions appear on the map, so the story cannot progress. So it means I have to restart the entire game.
When you complete Devon's mission I fought the Law..., he will tell Michael that he will get in contact with Solomon for him. After this scene, the S marker appears on the map. I decided to do Trevor's next mission Eye in the Sky and when the mission was complete the S disappeared.
Now no new missions appear. Solomon is in Michael's phone without having actually met him and a phone call with your psychiatrist has Michael talk about working with Solomon, which never actually happened.
I have seen online that a hell of a lot of people have experienced the same thing.
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Edit: Hindsight is 20/20 but to avoid this game breaking bug, do the first Solomon mission [B]Mr. Richards[/B] as soon as the S appears.[/QUOTE]
Did you try sleeping for a day or two or clearing your cache? Sometimes that causes the missions to reappear.