Hello~Normally those pessaries dissolve quickly, so I doubt if it would be completely excreted out. Try to insert one immediately after the BM, hopefully, that will give it more time to dissolve.
I suggest you to take a Neo Healar cream (https://hemorrhoids-help.com/) as it provides you a quick recovery.
The pessary is Hydrocortisone. I am also supposed to take Hydrocortisone as a cream before inserting the pessary. Of course the actual medicines have Japanese names.