We had a cat that liked to climb into the underside of recliners, sofas and box springs. Check all drawers and cupboards too.

Have you heard of the Elephant's Burial Ground? Maybe cats have a special place they go to die.

Have you found her? I once found my boston terrier closed inside my closet. She followed me so closely that when I opened the closet she stepped in and I didn't know. Until I couldn't find her thirty minutes later. I searched everyplace. When I finally picked up my care keys to search further afield I heard a little whimper from the closet.

My oldest cat, Sweetie Pie disappeared for a whole week during the coldest month of the year. I was sure I would never see her again, but ten days ago, she stood on the kitchen porch, thin and complaining. No idea where she spent her time but, she is happily sleeping in my bed again. I hope that your Lilly will return.

I recently did a housesit of two cats, one disappeared in a room full of boxes for two days. It briefly poked a head up when the other cat started calling for it but still wouldn't come out. Eventually to my relief on the third day it very rapidly came out when I called it by its nickname that I had only just been told of. It was then all over me like a rash and on my last morning at about 5am. started purring fit to wake the neighbours! Nicest of all was that after I left it spent an hour looking for me.

Maybe you taped her up in a box

Hope you find her.

Look in the most remote, darkest, quietest part of your basement. That's where I found my last cat, resting in peace.

I'm so sorry. My last cat would do the "hibernate to die" thing before she got too weak to move about, but she lived quite a while after that. She would go in corners behind desks, or in my closet and just stand with her head in the dark between the shelves but her body exposed, or under the bed. But I think she was experiencing a little dementia by then, too.

I don't think they look for a particularly complex place, just comfortable and quiet, kind of like when they go off to birth. I imagine it would be very haunting to not know where she is, or where she was when she died. She may wander back in view. At least I hope so, for your sake.

Look under the water heater.

I have not had one that went off to die, mine were always kept in the house and usually helped along the path by a veterinarian when it was the right time. I'm so sorry for your loss at a time like this.