Sorry to hear things went so poorly :( I feel your pain - it's the reason I ended learning to trim.
There are phenomenal farriers out there who do fantastic trims and there are barefoot trimmers who shouldn't be allowed near a horse's feet. Most in both camps fall somewhere in between. I suggest getting references from anyone you are considering, then following up by calling those references and seeing some of the actual trims. It's what we do when hiring most other pros so why should this be any different?