I'm so glad you got your puppy to the vet quickly. In CA, snail bait is the most common poisoning agent for dogs. Snail bait can contain molasses to attract the snails and it does resemble dog food.
We had LOTS of the slimy creatures. Beer worked in keeping the number down.
Here's one method you could try.
Use Beer to Get Rid of Snails in Your Garden - wikiHow
Hope puppy is improving quickly....it's so distressing when our pets aren't well.
Please let us know how things are going.