Can't pick up parcel at post office without peach/green notice?

With tracking from the shipper, I tracked my parcel via online . Said my parcel is held at a p.o and a notice was left. Maybe a note was never left or it flew away, dont know .I went to the p.o with id and explained my situation. But they refused to hand me my parcel. what is there left to do? I can't even pick up my own package.