I’m slow 😕 , so I don’t quite understand what happened. Can you give any more details? Is the button on a cushion? Is it on the frame/body? Did it fall through the fabric and is no longer visible?
I agree with Ron that pre-inspection is crucial with furniture as people often don’t know they have rips/tears/etc on furniture. I unfortunately miss stuff from time to time on pre-inspection, but then notice before I actually clean that part/piece of the furniture and bring it to the customer’s attention at that time. If it aint wet yet, it’s a lot tougher to pin it on me.