Yes, about a year ago we had our older cat go missing. She was an outdoor/indoor cat. (Actually she preferred being outside)
We went out of town for a couple days, had an 2nd floor window cracked open so the cats could go in and out. Came back, never saw her again.
Lately we've had a lot of bad luck with out cats. About a month ago, our other older cat passed. She had been sick for awhile, I came home from work one day, couldn't find her. Find her deceased under my sons bed. Now this cat was my wife's baby, she really really loved that cat. Breaking the news to her when she got home was horrible.
Now the third and last cat we have has been battling some illness since the move. Not eating, drinking, vomiting. Even vomiting blood. Trips to the ER, and so many trips to the regular vet, its been a roller coaster. But lately we think we're seeing improvements. So maybe we'll catch some luck.
So I feel your pain man, crazy how those little furballs become part of the family.
Also wanted to add, hang in there, she'll probably come trotting back in a day or 2 like nothing ever happened.