Warts are caused by a virus, and viruses - like many conditions that affect health - are susceptible to the immune system which has shown resilience when a person actively believes something will make them better. It's the basis of 'faith healing' and Voodoo and probably many other dubious remedies. Many GPs privately admit they have no idea at all what a patient is suffering from when they present at the surgery and they might as well give them coloured water for all the good they can do. But there's no cure for viruses at the moment, so burying your pet dog with a butterfly in its ear at midnight will almost certainly do as much good as anything the GP could give you.
In your daughter's case, N, I can only imagine the bloke thought he was being funny, but it might have been a good idea had he consulted her notes before trying a joke in poor taste. Verucas or Plantar Warts can be excised through various over-the-counter treatments, or surgically but they're classed as 'self-limiting, so it should go away by itself.
