As long as the transaction was made using the 'BUY' button then you are both covered by PayPal Protection, this means that the buyer can decide to open an 'item not received' or 'not as described' claim.
Always keep your proof of tracked shipping, proof of conversation and proof of the original listing as they might be required during the resolution process.
It might be that an item gets lost in the post, if so then you can open a claim with the shipping provider used.
If you're in the UK then tap here.
If you're in the U.S then tap here.
PayPal only accepts tracked postage as valid proof so we always recommend that sellers send any and all items tracked!