Oh, and regarding whether the pebble could pass, I would have thought it would based on its size (roughly the size of a pencil eraser), but for whatever reason it's not leaving her stomach. Which may be a blessing in disguise because if it got to her intestines and got stuck, she'd definitely need surgery.
There was also a chance she'd vomit it up (regurgitate), but that hasn't happened, and it needs to come out. I told her last night before I left that if she could just throw it up, I'd buy her 100 new toys AND she could poo on my rug that she loves to poo on, but I'm pretty sure she didn't understand.
She has been vomiting a lot, but no pebble.
The lesson: keep your babies away from pebbles!!!