I highly doubt that the vet knew what they were doing regarding frogs. This is common, unfortunately. Here is what I recommend: do what Eli said with regard to quarantine. Keep it in a quarantine container indefinitely and change the water every 1-2 days and the paper towel when it discolors. I and others actually keep white's tree frogs this way as their normal terrarium (I know some people don't approve of that). Keep the frog in the mid to late 70s - keeping it in the 80s can cause stress from the fact that it hasn't got a good appetite yet its metabolism is forced to work harder at that high temperature.

My big question for you though is ventilation: how much did the terrarium have? My white's live in a completely open top terrarium that only has window screen covering it. Excessive shedding can result from poor ventilation.

Lastly, what are the drugs in the cream they gave you - it should say on the container. Given the vet's approach, I'm worried they may be treating it like a reptile and many reptile medications do more harm than good for amphibians.