This is your tracking number

I was at the post office yesterday (of which more, theoretically, later), behind someone who was shipping a package. The clerk rang up the postage and did all those other fun things clerks do, before giving the customer his tracking number and saying, for the benefit of the slow ones in the class, "This is your tracking number." Of course I've heard this phrase many times before, but something in his intonation was such that I couldn't help elaborating to myself:

"This is your tracking number. There are many like it, but this one is yours .... Without you, your tracking number is useless. Without your tracking number, you are useless. You must enter your tracking number at the following web site" &c.