My dog swalloed the thin plastic thread(the one that comes with bin bags). I saw the last bit hanging out of his mouth but before I reached him, it was gone. We thought it will pass in his stool. It's been a about a week now and we have been observing his poop everyday but did not see it come out. There is no change in apetite or energy. Planning to take him to the vet tomorrow. Any advise on what should be done next? Are plastics visible in xrays?