Great post by Indy.
If there was absolutely no problem with the horse's feet, I wouldn't necessarily feel the need to be at the appointment. BUT since you are having isssues, a direct conversation with the farrier is critical.
Farrier day at a boarding barn is a busy, confusing day with lots going on. VERY easy for the BO/BM to neglect to tell the farrier some piece of into or for the farrier to just shoe the next horse brought to him without question.