I told a friend with three cats your story, and guessing it might have been spilled laundry detergent. Both of us spent a few hours, and some dollars, at Target buying the most lockable, spill proof containers we could find, and then transferring detergents, etc., into them.
Wel also reminded each other that accidents will happen to even the most careful mommies and daddies. I'm so glad Cello is doing better, and thank you for sharing your story.