You try to escape

You try to look around for anything that could cut the ropes holding your hands. Unsuccessfull, you figure that you have ****, but to escape with your hands still tied. With great effort you manage to get your hands your frontside and get your shorts back on.

With Marvin still sleeping you sneak out of his van. Even though you are pretty sure you managed to escape unseen, you still break into run towards the other end of the parking lot. Your sore ass, tied hands and wet cum ruining your shorts makes running a bit awkward experience.

You are almost at the opposite end of the parking lot, when you hear car starting behind you. You turn around to see Marvin's campervan exiting the lot. You feel good for not being with him anymore, but at the same time you realize that it was supposed to be your ride home.

You take a long look around. You have two problems: first you need to get your hands free, and secondly, you need to find your way home.

Even though you aren't completely familiar with the area you're in, you recognize the park and know that you could walk home through it. It'd be a long walk, but it's doable. You could also go check out those other cars in the lot. Now that you're closer to them you can see that there actually seems to be someone inside one of them. Maybe he could get you untied and give you a ride home?