https://www.usps.com/help/missing-mail.htm
Start by reaching out to your post office. I did this last week for a letter and got a callback the next day from the post office. They ask that you wait a week after initiating contact to file an actual claim. But I think they take the contacts very seriously and will help you out.
Start by reaching out to your post office. I did this last week for a letter and got a callback the next day from the post office. They ask that you wait a week after initiating contact to file an actual claim. But I think they take the contacts very seriously and will help you out.