They don’t “hide.” They warp out to a fourth dimension.
al we ever need to do to find jerry is whisper the words: tuna salad…
I had a California Kingsnake that was lost in my apartment for six months. A one bedroom apartment.
Since there is no single factual answer to the OP, let’s try IMHO.
samclem
My Maine Coons, Tibby and Libby are known to vanish into thin air for hours at a time. One day we decided to locate their elusive hiding spot. Hours of sleuthing uncovered their whereabouts—inside the living room couch. Check your couch innards, I’ll bill you for my finders fee 
Well cats do have their little secrets.
Glad to hear that all ended well.
Clearly kitty is letting you know how she feels about this strange new visitor. You’re going to have to give extra affection and attention to let her know that you are not “replacing” her.
Poor baby.
When I brought my two cats into a three-cat, two-dog household… two cats who’d never had to deal with dogs before… well, it didn’t go well.
I found my Duncan hiding in my father’s closet behind some boxes on the top shelf. I have no idea how he found that place. I have no idea how he got his fat butt up there.
dauerbach You may find that you need to check under beds and in corners to make sure that your cat hasn’t chosen to eliminate someplace besides the litter box.
We (foolishly) decided to get a dog once. We had two cats then, one was fine, the other terrified. After about a week my bedroom started to smell really funky. Couldn’t figure out what it was until I checked under my bed (one of Snowy’s favorite hiding places) sure enough that’s where she’d been defecating all week.
She had also been peeing on the leather sofa. Took me months to get the pee smell out of the sofa. Months and multiple cleaning products. I gave that sofa to my ex.
Good luck dog sitting.
Now there’s a happy ending!
I’ve done the “whole house cat search” gig and would have bet large amounts of money the cat was nowhere in the house. Only to have the cat slink out later, stretching and looking self-satisfied, from god knows where. It’s a cat thing.
cats do go incredibly high. rememer to look high, top shelf high, and low, under/in couch low.