If your horse has lousy feet this can contribute to lost shoes. The hoof wall needs to be strong enough to hold the nails and withstand the tremendous forces generated by the horse. Remember there are only six to eight thin little nails holding that shoe on. If the wall those nails are driven into is weak, it won't hold. Check out our FAQs on hoof supplements for some more answers.
All horses occasionally lose a shoe.
Once in a while is annoying but not a problem. If a pattern develops then you do have a problem that needs addressing. Your first line of defense is your farrier. Once this bit of detective work is done, then a solution can be found. The fact that your horse keeps losing shoes does not mean you have a bad farrier.