If you encounter the missions disappearing in grand theft auto five after completing the event called "Did somebody say yoga?", you can fix the game, and go on further with the story by doing this:
Switch between characters:
- switch between Michael, to Trevor and then to Frankie.
Try giving some phone calls.
- while controlling Michael try to call Trevor while you're being on a deserted road, somewhere in the city.
- restart the game, and then try to make Trevor hang out with Michael.