The centrum or the main cylindrical part of the mosasaur vertebrae is usually all thats left after 70 million years. The other parts of the vertebrae including the spinous , mamillary, articular and transverse processes that originally surrounded the vertebral foramen are rather fragile and usually missing. The vertebral foramen is the hole through which the spinal cord passes. If those folks you talked to do in fact have mosasaur vertebrae centrums with holes in the centers then you need to see them and get some photos. Off hand I can't think of what might motivate an Indian to drill a hole through a fossil vertebrae...........I can think of several reasons why a white man might do it. If money has been or is mentioned be very skeptical.