Liquid Plumr contains the active ingredients of sodium hydroxide and sodium hypochlorite as well as a surfactant (soap-like substance that breaks apart grease and protein material).
All of these are gastrointestinal irritants, and the first two are acids which and can lead to symptoms of drooling, vomiting and diarrhea, ulcers and secondary strictures all of which can contribute a loss of appetite. We do not recommend inducing vomiting in cases of possible ingestion of these types of products as that only leads to further irritation/ulceration of the esophagus.
The baby bunny could certainly cause stomach upset due to eating an unfamiliar food and irritation from eating fur and bones.
He may be lethargic simply from eating all sorts of strange things his gastrointestinal tract is having trouble processing.
At this point you just need to watch Kairos for any further symptoms while treating him symptomatically.
If he starts to drool or actively vomit, has a tense painful abdomen or has tarry stools (indicating digested blood) or large amounts of frank blood stools he should be seen on an emergency basis.
We can do some things at home to ease stomach and gastrointestinal irritation.
To try and settle his stomach you can give either:
1) Pepcid-ac (famotidine) at a dose of one 10mg tablet per 20 to 40 pounds of body weight every 12 hours.
2) Prilosec (omeprazole) at a dose of one 20mg tablet per 40 to 80 pounds of body weight every 24 hours.
These will reduce stomach acid and should help settle his stomach. These can be used for several days as necessary as they are quite safe.
Then feed a homemade diet of 1/3 boiled hamburger or white, skinless chicken, all fats and juices drained and 2/3 white rice. Add 2 to 4 tablespoons of canned pumpkin, (not pie filling, just pumpkin), to each meal for fiber to push through the bones, hide and fur. Feed small meals several times a day.
Once he's feeling better then start mixing in his regular food, adding a little more regular and less bland at each meal. It should take a week to get her converted back to regular food.
If he beguns vomiting, even after the acid reducing medication is given, refuses to eat or has explosive or bloody/tarry diarrhea it is best he see a veterinarian for an examination, injectable medications, fluids, and oral medication like sucralfate to coat his gastrointestinal system.
But if he shows no further symptoms you might be able to nurse him along at home.
Let me know if you have any questions.