My neighbor has my mail. What should I do?

Last week on Friday, I ordered a limited edition Johnny Cupcakes shirt, online. On the site, I requested it to be shipped to my P.O. Box, but instead of shipping it there, it was shipped to my house (they apparently don't ship to P.O. Boxes, so they did a bit of research to find where I am living.) Anyway, I received an email saying that it was delivered to my house at the front door. But, of course, there was no package on my porch. Where my house is located, you must go down a right-of-way-driveway to get to it. My neighbor's house is at the top of the driveway. My neighbor is extremely difficult to cope with; he purposely blocks the driveway with branches, rocks, etc. Lately, he's even been leaving carpenter nails in my driveway! I don't even know why this even started. Many other things have occurred but, it's impossible to list them all. Back to the main subject, discovering that it had been delivered, I decided that I have to talk to him (my neighbor) to see if a package arrived at his house. He flat out told me no, and said nothing else. After making some calls to Johnny Cupcakes and the UPS, we have discovered that it was indeed delivered there and now, the UPS is going to question him about it today. What I'm worried about is, what if he says no again? Will the UPS be able to do anything about it? I ordered the shirt for my daughter and she's a diehard fan of Johnny Cupcakes, and I hate seeing her like this. There were only 300 of these made, and now they're out of stock! Is there any legal action I can do? Any action at all? Please, I really need some advice.