It’s easy enough to rule out a prankster. Check the pressure on Saturday morning, Saturday evening, Sunday morning, and Sunday evening. If it’s going down steadily, it’s a leak.
Since you mention quarters, I’ll assume you’re driving to a gas station on that tire. That will quickly damage the sidewall and make the tire unsafe, so you’ll want to stop doing that.
You should be able to find the leak by spraying soapy water over the tire and looking for bubbles. If you really can’t find it, have a local tire shop put in a new valve stem and clean up the bead area to see if that makes a difference.