Oh my gosh! How awful! If that vet is too busy, call another one. maybe feed him a can tuna in oil, the oil may make him pass. my cat used to swallow rubberbands and I would feed her the food that made her poo and it helped her. ( Now, I ban any rubberbands at my house. ) silly cats!
how much string did he swallow? I say call another vet.
I just found this............>>>>Common household items such as embroidery floss, spools of sewing thread, rubber bands and even dental floss can be life threatening for a cat. Sometimes the thread or string can pass through the cat's digestive tract without serious injury if it's small enough. Unfortunately that is not always the case, especially if the cat swallows a large amount of string, twine or thread. Just imagine how much sewing thread a cat can swallow from even a miniature size spool of thread. The string or thread can get wrapped around the tongue and if swallowed can wrap around inside the intestines and cause the cat to become very ill and will lead to eventual death. The thread can even cut into the intestines. Surgery can sometimes be the only chance of survival and that isn't always successful. If you suspect your cat has gotten into some type of thread or string, be alert for the first sign of problems. If your cat begins vomiting abnormally, (more than the usual hairball) diarrhea, or constipation, lethargy or any erratic or unusual behavior, take her to the veterinarian quickly and assume she swallowed the string. The longer you put it off, the less chance the cat has for survival. <<<<<<