PaperTsubaki When a buyer escalates a dispute on PayPal, it's the responsibility of the seller to prove that they did indeed deliver the item/service, not the buyer. If you want, you can include screenshots of your correspondence and just mark the dispute as "service not rendered"/ "requested refund but seller refused" in the comment if you choose to escalate. The seller will have to refund you or fight the chargeback with evidence.
Worst case scenario is that the artist does give you a piece of rushed art to claim that they did it, but I feel like a chargeback would still be justified if the quality of the art did not reflect the samples given at the time.
I hope you get your art or a refund, these types of transactions are always so unpleasant to deal with. Good luck!