I've had two stool tests for parasites that both came back negative because I'm sure I've seen them in my stool. My doctor advised me to extract anything from my stool that looks like a worm and bring it to her to see. Sometimes I guess this is the only way to confirm parasites. What you saw might have been some kind of large mucus discharge. Either way, you should probably address the physical symptoms with your doc before worrying that it's a parasite. There are more serious causes of abdominal discomfort than parasites.
Welcome to the gastroenterology community! I would recommend that if this continues that you see a doctor about this. I thnk it is more likely to be something else than a tapeworm, so I don't think you need to be overly concerned about a tapeworm, but I think that it is still best that you see a doctor about this.