Justin,
We go into pet stores too - trying to educate store operators about chameleon care. Often we see a suffering cham - and "rescue" them. Most times, the store owner will settle for cost - to sell it.
Just today we came home with a young pair of cb deremensis... the female is very thin and her tail may be necrotic. The male only has tiny nubs for horns... so hopefully we can turn them around and get them healthy again. Being out of an aquarium is the first step - next is feeding a proper diet and fecal exams.
A couple of stores have asked if I would work for them - but since we have our hands full with our breeding colony and importing - it's just not possible for me to squeeze out any time for working elsewhere.
If it is stressed and has spots, it could be a deremensis or a flapneck. Check the species pictures at AdCham - "chamaeleo"
http://www.adcham.com/html/taxonomy/taxonomy-map.html
Be sure to check the husbandry requirements.
Many times with "rescues" we have to tube-feed. We use pedialite; crickets; superworms; waxworms; and vitamins (a bunch); add some Repti-Aide powder and mix it all in the blender - on liquify. This provides a balanced thick food, that can be fed though a syringe & tube. It is tricky business - but a vet can teach you to tube-feed safely. Keep the cham warm too (check temperature guidelines - stay close to ideal basking temps). Mist often, moist surroundings can help rehydrate. Chams can absorb moisture through their nasal lining too.
Best of luck if you decide to "rescue" the little guy.
Morgana - Reptayls, Ltd.