you have 45 days to put in a claim through paypal, when you do they will put a hold on the funds in the sellers account (whether ebay seller or not), if the seller cannot provide proof of an online trackable service then paypal will find in the buyers favour without fail.
You are right but you are only covered by PP's complaint's policy unless you buy the item off of ebay (in which case you get full buyer protection
) so even if PP finds in the buyers favour they are not guaranteed a refund unless there are funds in the sellers account. From PP's website
Even though you may escalate an Item Not Received Dispute to a Claim, you are not guaranteed a recovery. If the Claim is decided in your favour, your recovery may be limited to the amounts that PayPal can recover from the seller’s Account.