There is always a spot for a tent. I would have just set it up on some grass area at the park. Once the ranger comes you can tell him that you're 45 miles away and don't want to ride at night. Most likely the ranger comes by in the evening and by that time I doubt he'd want you to take the risk out on the road. Asides I doubt your tent is a very large one.

Otherwise, once it gets late you can check ask people politely if they know of a spot for a tent for the night. Don't ask for a camping spot since you are not camping. (Camping = big tent/rv, bonfire, loud people, etc.) Once it's getting dark find a public grass spot that's suitable for a tent. You'll be tearing it down by early dawn and most people will notice you. Just follow the no trace philosophy, cause little impact, and respect private property signs and fences. If in doubt ask at the nearest residence.