The errata sheet was with the
MM when I received it.
Since it was not available at any local stores when it was released, I prevailed upon the kindness of an aunt of mine living in downtown Montreal.
She lived about three blocks from a game store and I had her pick it up and send it to me by bus (Voyageur to SMT). I picked it up as soon as it arrived and the there within the front cover was the errata sheet. I assumed that it had been placed there by TSR and not the game store, but the only other one that I have personally seen since then belonged to a friend who picked up their first edition
MM in Halifax.
To be quite honest, with the amount of use that I got out of that book, I am rather surprised that I never lost the errata sheet, or used it for scrap paper.
JasonW