I've done little more than a quick drive through Joshua Tree, but I expect that like most national parks there's not a lot of options for how to get from point A to point B on the roads. The vehicle in question is Corolla, so it will not venture far off pavement.<p>1. You leave a note or maybe several of them. If things go well you will be reunited with your partner soon and you can drive back to clean up your litter. If things go poorly, it's a clue to the search party that you aren't lost in the back country. If it's a popular trailhead, there will be a log book there. Make a note in it with the date, time, your phone number, and your plan.<p>2. You start walking to the main road but only if that is the same route that you expect your ride to be coming from. Do not accept a ride from anyone except a park ranger that can radio in to head off a search party. You are not the first person that's been in this predicament.<p>3. While walking, when a car approaches hold up an empty water bottle as a sign you need more water. Decline any offer for a ride, but graciously accept water, gatorade, and snacks.<p>4. As soon as you get a connection to civilization, try to get in touch with your ride. That will most likely fail, in which case notify the park rangers of the situation. Your ride may need a rescue somewhere too. This is especially true if this not-a-hiker person decided to try to track you down in the back country as it was getting dark.