Glad you've not noticed a change, that is probably good right! I think the Gut microbiome extends further than just the large intestine, you've probably got some bugs hiding out somewhere in the system :) https://www.newscientist.com/round-up/microbiome/
You still have gut bacteria in the small intestine, and they're probably as important as the ones in the large intestine. I can guarantee you that without both the small and the large intestine, you do notice a difference (but unfortunately for reasons more serious than just not having the bacteria). Glad you're adapting well to living without the large intestine!