PUPPY SWALLOWED LATEX BALLOON!?

I have a Shihtzu puppy about 5 months old. She just swallowed a small (think infant's head) balloon, no helium. I've called the vet and she said to wait a while and watch for signs of lethargy and lack of appetite. Is there anything I can do, maybe some safe home remedies or additional signs of danger? Or do these sort of things usually just pass through the system?