Yay! I happy to report, that Will's plan to sleep light so that he might hear Tabitha worked. He heard her early this morning, and although could not catch her, at least we knew she was nearby. After a shower (which apparently scared her away from the open front door), I went outside and looked around again. I opened the shed with the electrical box, and was hissed at. When I looked up (I had opened it to see if she was hiding under it) There was Tabitha, crouched on top. As soon as I started talking to her, she started scolding me soundly. I had to pull her out awkwardly, but once I had her, she did not struggle too much, and allowed me to bring her inside. She got a nice wet catfood treat (half of Yorick's breakfast) which she scarfed down, and has graced my lap a couple time since.

Edited to add photo of her dumping 3 days worth of shedding on me.