Ash here from the Shopify team. Welcome to the Shopify Community!
I definitely appreciate the concern with this situation. I too would want to make absolute sure that I'm receiving the payments I'm due. I'm happy to help out with this. The first step I recommend is heading over to PayPal and logging into your account. You'll want to check in there if the payment has been received for this order.
I hope this helps, and feel free to reply back here if you need any further guidance with this situation!