Once the Not As Described case is opened, the seller must refund. If you wait, you will get a defect on your account. So do not delay in refunding. Buyers are not required to prove what they say is true, eBay gives them the benefit of the doubt. So the buyer does not have to supply evidence or pictures, etc. It would be nice, but they don't have to. Ebay places the buyer's interests first. Sellers must watch their own backs.
But there is still something you can do. Contact the buyer and tell them you are shocked that someone has rifled their mail, and you won't rest until you get it reported to the authorities and get to the bottom of the matter. Ask for them to save the packaging to present to the postal inspectors and how much you appreciate their cooperation. Reassure them that theft of mail is taken very seriously. It is a felony.
The reason for doing this is two-fold. First, if they are innocent, they should have no problem with it, and it is the correct action to take. Second, if they are guilty of pulling a scam, this will make them nervous. Scammers want to fly under the radar, so you want to be sure their names are attached to the report. Using the mail to commit fraud is also a felony. It won't get your money or item returned, but it could prevent this from happening to another seller if the buyer is running other such scams. You can make a rifled mail report online.
Good luck and sorry this happened to you.
