I have also seen a low bounce rate for a site only to find out that the coinciding amount of visits & traffic was low as well. First thought was that it was very niche or specific keyterms. Wound up that the analytics code was stripped from most of the website pages as you found.
I would have turned that campaign back over to whomever was doing it prior if 1.5% bounce rate was accurate. In fact, I would be calling that person day in and day out...lol Glad you found the issue though.
"Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime." Chinese Proverb