Pwray,
The tooth test, however you do it, cannot replace genuine magnified direct examination of the pearls in their entirety as a test of whether they are "real". This needs to be done by an expert! I doubt your gift shop expert used a loupe and closely looked at the pearls, including the drill holes, before passing judgment.
The manmade nacre used on the best faux pearls can be made up of crushed pearls, fish scales, etc, the top faux pearls are "dipped" multiple times in the "nacre" to give a depth and realistic finish to the beads. They are very, very pretty, and fun to wear because they do look quite real, Jackie Kennedy and other famous women of the past wore their faux pearls as proudly as if they were authentic SS or Tahitians.
If they were real, they would be top quality white South Sea, having been sorted out from tens of thousands of pearls over several years to match size, color, quality.
It would be wonderful if they were genuine and valuable! I wish there were more indicators than the tooth test that they were so!