[Patrick_cpg]

Take photos, and make a claim at the post office ASAP. Even if you don't get reimbursed, it will put them on notice in case this type of thing is happening to your neighbors.

[d0dgerfan1979]

I talked to my aunt who works at the post office as a carrier and she says if an item has been opened or "knifed", to avoid the claims process, the procedure is to return the item to the sender as "undeliverable" with a note that says the USPS will not accept open items for shipping. In certain circumstances the USPS will also not accept an item in a box or envelope that has visibly been torn open, then retaped. According to her (my aunt the postal carrier), if the item made it to your door, it would have had to have been sealed still, meaning someone would have had to have opened it AFTER delivery. This could have been your carrier (a substitute carrier on a route most likely), a neighbor, a passerby who may have seen your envelope, or a family member/roommate/resident. If it made it from door to door (meaning from shipper to recipient), the post office will most likely deny any claim based on the aforementioned policy. That being said, that doesn't mean you shouldn't file the claim. Get a record of it. Tampering with mail is a federal offense, so you may also file a police report ( should you is another matter altogether).
The bottom line:
Take the seller's offer of a $5 refund. It will take far less time and create far less headaches for you.