I know I've seen people say they keep them in the fridge (not the freezer). I remember one person said she kept all the little plastic containers the worms came in because they were the perfect size and no one in her family would open one by mistake.
You might call the vet's office and ask what they recommend.
Ok called and they said to put it in a zip lock if its going to be next day. But if its more than a day or 2 it would not hurt to put it in the fridge.