I see your point on opening a dispute, although I most likely would have contacted your seller directly first, just as a good faith gesture. Anyways seeing as this is a craigslist purchase things are a bit different than if you purchased from eBay or here. So opening a dispute was most likely a good call to get communications rolling and documented. As craigslist it self states on their page to never buy anything sight-unseen. If you haven't seen what you're buying, there's a good chance it might not actually exist. Well unless it's a weird piece of fake broken plant, it obviously exists
As far as what Paypal will do, you have 20 days after opening the dispute to escalate it to a claim. During the Claim process, PayPal may require you to provide documentation to support your position. You may be asked to provide receipts, third party evaluations, police reports, or anything else that PayPal specifies or relates to the transaction. Please be aware though they may require you to ship the item back to the seller at your expense, and to provide proof of delivery. I am not saying this will happen but it could, it all depends on how your seller is going to handle it and how Paypal views the dispute.
I do hope though you are able to get this resolved quickly. Please keep us posted, as I myself am curious how Paypal will handle it.