I think it's because they aren't sure if your serious.
I've listed stuff on CL, lots of times. I've even given stuff away for FREE, something I do a lot.
If someone is calling from 2 hours away, I'm automatically suspicious.
Either they don't know where I am from them
OR they are a fraud. Most of the time it the first one.
If one can pay via paypal, but then you want to make sure that the guy selling isn't a fraud. SO.... yeah,
Next time, try offering the person $20 extra as an incentive to hold it just for you. It's a small price to pay for quarantee.
Be grateful that these people were nice enough to call you, at the last minute BEFORE you started driving.
Best of luck to you ! You'll find what your looking for, perhaps at the most inopportune time. And it might not even cost you any money. Be patient, and keep your eyes open for opportunities.