What happens to a package set to be delivered to a non-existent address? (Shipped through USPS)

I recently ordered a package and accidentally set it to be delivered to a non existent address. The website has no "cancel", or "re-route" buttons, so I emailed the company. They said it was fixed, and the address was changed on "the back end". The problem is, whenever I go to their website, it still shows the non existent address. Say they didn't fix it, what happens to the package? Will it be returned to the sender, or will it sit in my local PO? If so, what do I need to prove it's my package? I do apologize for the paragraph of a question, I wanted to cover ALL of my questions. Any advice is appreciated.