I presumed it wasn't used simply because in the storyline, Liz never knew Barnabas' secret.
And sort of along that same line, I never understood why the Philadelphia Gum Co. felt the need to doctor this photo to add fangs in Barn's mouth:
(http://www.dsboards.com/images/Barn-Liz.jpg)
But then they also doctored his eyes and outlined the trim on his coat and jacket. (And they did similar things in some of the other photos used for that pink card set.)
Somewhere around I have a version of that photo that's not doctored, but at the moment I have no idea where that is. Though I'm sure I'll come across it some day when I'm looking for something completely different. [santa_wink]