Figured I would update you guys with what's been happening with my own attempts to dispute the charge. PayPal auto-closed my dispute because I was well outside the 45-day window (I paid on 5/15). I called my bank to see what my options were. One thing they clarified for me is that it's 60 days from the statement cut date that would include the transaction. I don't know if that's the same for everyone, but if it's the same for your bank, then it'll give you a few extra days to get your dispute in. They looked into the options for this, and unfortunately they could not dispute the charge directly. Technically, since the draft from my bank account to PayPal was authorized, then the only option for me to do was to fill out papers alleging that the PayPal draft was not authorized. They advised me that if I filled out that form, then PayPal will probably come after me for the money. I decided to do it anyway, because at least then PayPal will have to talk to me, which they won't even do right now because it's past their 45-day limit. They agreed with my logic, so I filled out the form and faxed it in. We'll see what happens.
Hopefully I can convince PayPal to open a dispute despite the time difference and go after this guy. Oh, a tip for anyone else in the same boat, if you talk to PayPal, I would recommend avoiding terms like "group buy", "pre-purchase", or anything else that suggests this was a payment for goods he did not have in-hand. They seem to look down on those things, so it would probably just be best to stick to "I paid for a product, he kept promising it was on it's way but stalled saying there were shipping problems or other things which is why it went past the 45-day limit." Then hopefully they'll do something for us.
