When we got in the little room, she hopped out of the carrier and inspected every corner of the room. In detail.
She did not knock any of the stuff off the sink cabinet, though and I realized that that was one of the causes for concern. She has a Knock Off Whatever daily quota that she has been ignoring.
Anyway the vet discovered that she had a little fever but no other symptoms of anything at all. He said we could run some tests on blood work, start her on antibiotics, or just wait and see if she just works herself out of whatever it is. I picked door #3.
She was happy to get home and has now disappeared. Her fancy new collar has a bell but something about the way it's positioned, I can't really hear it jingle when she moves so she's back in stealth mode. It does click on her water and food bowls so at least I know when she's eating!