My husband took the stone to our vet, and she is sending it out for testing. Of course, Abbey went potty no more than 10 minutes after he left, so I have to wait for the sample.
She wants to see Abbey too, because she said if there was 1, there could be more.
Abbey seems fine right now, just playing with Riley and Jada, so I don't think she is in any pain--I could really tell she was miserable last night.

I'll keep everyone posted.