What if my customers invoice/purchase was billed/delivered to a Dutch/European address? /

If your customers invoice was billed to a Dutch/European address, or if the purchase was delivered to a Dutch/European address, your customer can still get a VAT refund if the invoice has been stamped by customs. 

To be eligible for a VAT refund, your customer must export the goods to a country outside the EU. If there is a customs stamp on your customers tax-free form or on the invoice from your store, the export of the goods has been checked and validated by customs and you are allowed by the tax administration to process the VAT refund request.

You can read more about the customs stamp and customs procedures to ensure your customer has exported the purchase here.