UPS lost my trade-in iPhone

Apple sent me a box and packaging to send my iPhone to Apple as a trade-in. One week later, the status has been stuck at "A damage has been reported and we will notify the sender" for several days. An update from UPS says, "Merchandise is missing. UPS will notify the sender with additional details. / All merchandise missing, empty carton was discarded. UPS will notify the sender with details of the damage."

Seems suspicious that if the merchandise was missing they discarded the box, right?

Apple says it hasn't heard from UPS yet. What can I do?