USPS lost my package - what should I do?

dude, it might not have been lost. Someone could have taken it after it was delivered, but if usps did in fact lose the package then I would call someone who works for them and complain and I would try to get answers

If the supposed delivery was today or yesterday, wait for one more delivery attempt. It's possible that what the status message means is that it went out for delivery, but that it may not have actually been delivered if it needed a signature and you weren't home.

If the delivery attempt is more than a day or two ago, call or visit your local post office and ask them to check their storage area, and also stop by your neighbors to see if they got it by mistake.

If the package was insured when it was sent then it can be replaced, if sent by regular mail then you are out of luck. Fedex and UPS insure the first 100 dollars on every package so have it sent one of those ways next time if you can.

Ask the Post Office to Investigate. It is a Federal Offense for someone to steal your mail