It was funny when you mentioned this. Back in college days, I temporarily lost my 12 foot Burmese to this exact opening except it was in a bathroom cabinet floor. I used to feed her in the bathtub and she killed the rabbit but didnt eat it immediately. I was in another room of the apartment with the bathroom door closed. Came back in to find the rabbit in the tub but no snake. I found her the next day only because I was sitting on the throne in complete silence and heard her sliding on the floor in the cabinet that housed the sink. Had to take the floor of the cabinet up to get her out of there.