My tax refund check got lost in the mal, what do i do?

my federal tax refund was mailed out last friday march 4, my sisters was mailed out the same day, and she lives in the same complex as me, she got hers on monday, i waited until yesterday friday the 11th 1 full week, called the irs they comfirmed i had the right addy, usps, supervisor agrees it prob got lost or stolen, what can i do the refund was sent from andover ma, what should i do or can i do?