Poop in rectum post defecation. Or ibs?

Hello, I'm 41 with the correct bmi. I have been diagnosed with IBS by my gastro who had 40 yrs exp and have been taking meds on and off to avoid symptoms. I take fybogel everyday. Today I had constipation. I pooped and then applied fidonal ointment to help with pain. When I inserted my hands inside to apply the meds, there was lil poop that stuck to my finger. I did feel complete after defecation but this happened after I applied the medicine. Is it normal for a Lil poop to stay in the rectum like that due to constipation or ibs? This is the first time I'm noticing this. I have ext hemorrhoids. I don't have blood in poop or pain or other symptoms. I was asked to take pruvict for a month but I could not as it gave me 7 times loose motions for 3 days and I had to stop. Pl advice. I'm a vegetarian and Gen stick to bland food only. I'm always afraid of colon cancer although there is no history in my family. Would be grateful if you could alleviate my fear. Thank you.