Carolyn,
I would ask the vet why they gave you a powder rather than measured oral suspension dosed for weight. If they did a fecal. Ask if it could be a bacterial infection? Coccidia? Crypto?
However...if that store has had a history of crypto the vet probably knows it is hopeless, and nothing you do will matter.
Unfortunately many vets are just not educated about how to care for reptiles. They give you panacur and send you packing...you can get panacur at Petco yourself (under the name "Safeguard"
, and take a wait-and-see approackh to see if it helps... Trouble is, babies need the proper meds quickly. Babies don't have much resilience, and a bad infection often does them in. Plus, they are so small, you need to be very careful with med dosing, or the meds could do them in. I am sorry, but you need to be prepared. Do what you can, but don't blame yourself if the animal dies, you did all you reasonably could. At least you can get your money back. Next time, buy a HEALTHY, well-started animal from a reputable small or medium/large breeder online or at a reptile show, or a reputable reptile pet store if there is one near you. One that is already established with fat in the tail, and at least 5" long. It may been like a lot to pay $30 shipping on a $30-$50 gecko or two, but it's still less than the cost of one vet visit for most people. And can you really put a price on avoiding heartbreak, or on your pet's heath?