Here is information from the AVMA on declawing.
http://www.avma.org/issues/animal_welfare/declawing_bgnd.asp
Claw regrowth—Claw regrowth is a consequence of incomplete removal of the ungual crest, and can result in abscess formation and pain.1,2,11,12,28,30 Approximately 3% of declawed cats exhibit claw regrowth,30 but a 10% incidence was reported with a technique that left the flexor surface of the third phalanx in situ.11
So, it sounds like you should see another vet about this and monitor for signs of infection or pain.
Also, this is the AVMA's position on feline declawing:
http://www.avma.org/issues/policy/animal_welfare/declawing.asp
Basically, their position is that proper nail care is usually sufficient and declawing should only be a last resort if the choice is between declawing and euthanasia.
Unfortunately, a lot of cat owners lack education on how to encourage a cat to use approved scratchers and to train them to avoid things you don't want them to scratch, or on how to properly trim the nails on the cat to keep them from being destructive. Probably the worst culprit are those horrid, commercially available, short, carpet-covered scratching posts that just aren't rough enough to appeal to the needs of the cat...not to mention train them to scratch on carpet (how would they understand that carpet wrapped around that post is okay, but carpet elsewhere in the house isn't).
I felt bad enough putting my cat through surgery to get her spayed, and that we know is not only to prevent pregnancy and all the nasty behaviors associated with heat, but also increases the lifespan of the pets (dogs too) and eliminates the risk of a type of uterine infection that dogs and cats are prone to getting that can be life threatening.
Tail and ear docking are also not required for domestic pets either. The only species I know of where tail docking is appropriate are in sheep and pigs. In sheep, when they are out on pasture, they can get maggots and infections up under their tails if they are not docked, and in pigs, they have a bad habit of biting each others' tails (if they weren't docked, they'd be bitten off, with all the risks of infection that comes with, so better to dock them). Tail docking and ear cropping entirely for aesthetic reasons seems cruel to me.
Though, if a cat were clawing at people, and removing claws might not make the cat nicer, but would mean you could keep the cat because it wouldn't hurt when it tried to swipe at you, then that might be a situation where it becomes a trade-off between declawing vs euthanasia.