Does she like to crawl in drawers or cupboards or anything like that?? My mom's one cat did that a lot, and when they thought Lucey was missing one time, here she had gotten in one of the drawers in their clothes closet and no one saw her go in, and the drawer was closed. They found her sleeping peacefully when they ripped everything else apart trying to find her.

My cat Boris will hide in weird places too.

Hope you can find your kitty, it's scary and frustrating when they are missing.