Dude, i believe you are in the mission for setting up a heist possibly? if you have to hide the get away car, grab a random car off the street, and it should say "something something ring michael to confirm location of get away car", pretty much all you do is park the car somewhere un-obvious and ring michael and his get away car option, if it doesnt let you, drive further away, because there is a distance it has to be to the heist site.