Well it's been 3 days and still no earring.
I began to wonder if maybe she didn't swallow it after all so I searched under the sofa pillows, under the sofa and didn't see it. I took the suggestion of putting her poo in a zip lock bag and doing the "squish test"
and haven't seen it there either. She's doing great though otherwise so it's still a mystery. And I too noticed those cubic zirconia ads that night and felt like I was in the twilight zone!
ETA: Wait a minute I see the CZ ads now! I swear I didn't see them before.