If you see anything in your stool, get gloves on and get it out, rinse it off i sink and lay on paper towel and than DISINFECT EVERYTHING. Inspect this, if it looks like undigested food tomatoe or bellpepper etc. you know what it is. If you dont call your dr and pick up a stool test and hve it examined by a pathologist. Your body is cleansing itself, it sheds the lining of your colon and thats a good thing. Better out than in.
I would say check if you have more accidents like that. Have you had tomatoes or red pepper the day or two prior to your bowel movement? It is common to have undigested pieces of vegetables or fruit in your stool.