This has not taken place, but I was curious about what happens when an order is deleted on the orders page. Is it removed from the database or is there a way to restore it manually? I have a little mysql experience and was interested to know if it was possible to restore a deleted order.
Only from a previous backup that you "“obviously” did the day before
If he created an account, you could contact him. If he used PayPal or Google, the contact information is still there. Your email should have the order information.
You should receive the email when they order to your website. Create the new account with the new order number and email them to tell him, you have now new order number.