set it aside...it'll dry out eventually (as long as he didn't pee on it) my kids (decades ago) threw a clear toothbrush down the toilet & flushed...took me 3 pull offs of the toilet to find out what the problem was .
Haha, it was clean water, and only about half a roll. I always buy in bulk so had 36 rolls in the basement before I even heard of covid-19.
I saved it to dry, will probably use as fire starter.
Lots of things go down toilets. Long ago one of my kids flushed a 6" long toy motorcycle down--and it just went right through.
Tough luck, kid!
I know a plastic toy tractor went down ours a couple weeks ago... we have a lift station in the backyard because we are lower than the city sewer. Fingers crossed it doesn't cause any problems there...