Bought used laptop, too late to return, missing serial number.

Question

A while back I bought a MBP 17" off a power seller on ebay that buys out of warranty macbooks and repair them independently for resale.
the one i bought is missing its serial number, and i have no way of recovering it. since then i've bought one straight from apple, but i'm still determined to get to the bottom of this.
is there anyway recover a missing serial number from an MBP that has had its logic board replaced (as I was informed by the seller)?
I tried returning it before but they only offered to repair it once it got a kernel panic etc. I denied that offer because I figured I'd never see it or my money again.
Thanks.

Answer 1

It's true that I'd want to see a serial number on any Mac that I bought — not because it would do me any good, but because not finding one would suggest that the machine might have been stolen. Of course a machine with a number could have been stolen too, but it wouldn't actively suggest that possibility to me.
Whatever the case may be with respect to that, having a serial number wouldn't win you any benefits that I can think of. As a policy matter, Apple won't repair a Mac that has no serial number. But because you have no Apple warranty, no Apple repair would be free even if you had a number, and an independent service provider's work is usually less expensive than Apple's.
There is a curious fact to note here. When Apple replaces the logic board in a Mac notebook during a repair, the serial number is sometimes (always?) removed from the machine as part of that process. I don't know why. This is sometimes done as part of a warranty repair, and obviously Apple is still obligated to repair that machine, despite its lack of a serial number, if another failure occurs during the warranty period. This suggests to me that Apple must keep some internal record of the machines from which it has removed serial numbers, so it will recognize them if they appear again in the warranty repair stream. But I've never heard of Apple putting any label bearing a new number into such a machine.