I'd say if you can get the address to where it was sent, take a trip over to the dudes house and pick up whatever it is that was mailed to you. But, I'm assuming you already know where the guy lives.
As for the lady behind the glass, I don't know. I'm thinking you could have came back at the end of her shift. Waited in the parking lot (of course in a ninja suit, she can't be recognizing you now) and followed her home. Then when it was late enough at night, break into her house and find the bitch. Once you've located her, give her the
ULTIMATE NINJA PUNCH OF THE GAWDS TECHNIQUE right in the taint!! Your mission will be complete...and I will give you your next assignment....
Yes folks, I'm bored at home...wachya gonna do about it!