"Foreign substance" -- probably one of those "two all-beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun" thingies that someone smuggled in there.
Didn't take long for that to transit the intestinal canal it would seem!
20 posted on 05/25/2023 1:36:48 PM PDT by ExSES
(the "bottom line")