I am not in the US so may not be best placed to comment on your domestic shipping situation but from what I've read on here USPS is a shambles most of the time and a confirmed delivery doesn't count for much apart from probably fucking up your chances of getting compensated by the vendor. If it doesn't show the best you can do is talk to the vendor and see if they are open to a reship/refund or whatever, I would say that it is highly unlikely the feds will come knocking for a 1/4 oz of green, at worse a letter IF (and that's a big if) it has been intercepted. Using a crystal ball would probably be more reliable that USPS tracking as many people have stated it rarely reflects the true status of your shipment, take from that what you will and I hope it turns up.