I'm a member of a German cat site with a "resident" vet, and checked out old posts just out of curiosity. I found posts about ruptured diaphragms regarding cats who'd tried to slip out of windows tipped open from the top, who'd been the victims of doors slamming, and one who'd fallen from a third-floor balcony. It might very well be that the potted plant fell on Persil. Her problem may have been due to a congenital defect, or to a simple mishap. I really hope that she recovers fully. I know she's had a very rough time (not to mention you), but this is so much better than FIP! Good luck, Jenny, and thank you for being there for underpriviledged creatures.