What were the refs supposed to do? Did you want them to stop the game and call around the US until they found the proper NCAA official to tell them whether it was ok to have that on the shirts or not?
Vandy may or may not have been playing dumb, but they were told the unis were approved (by the NCAA by the way) and were not specifically told the "Anchor Down" was not approved. In this game it didn't matter either way, but I would rather see games decided on the field than because someone had some words on the back of their jersey so they got penalized for it.
Refs were supposed to stick to their guns, enforce the rules and let Vanderbilt play under protest if they wish.