But probably not too big to get scent on it and later be swallowed intentionally by the snake. I NEVER feed my snakes in their own enclosure or in any enclosure with substrate of any kind. I separate them and feed them one at a time in a bare container or I feed them outside on the lawn. If I were you, I'd feed very small meals, and only soft stuff such as pieces of fish and see if the snake doesn't poo, until you can figure out exactly what's going on. It does sound like there is a piece of something in there such a piece of bark. It may or may not be causing an impaction right now, but the risk is high.