This is exactly why my animals will never go to a vet...
How or why a vet would dose a reptile with worming meds and antibiotics without knowing if there is even a problem to be treated, is beyond my understanding... Most of the time these unnecessary doses of meds do more harm than good...
In all honesty, I think you could have avoided the vet bill because the vet pretty much told you what you already knew... Seriously, heat that animal up and make sure he is well hydrated and you will see a big turn-around...