Missing Kitty

Bri (the cat) is missing.  Well, not so much missing as...well, first i need to explain that our "custody" of her has been sort of a grey area.  She technically belongs to our neighbor's daughter-in-law.  When she and his son moved in, they brought along this cat that was her mother's, because the old lady didn't want it left with her.  They didn't feed that cat, when she found us she was skinny and sick-looking (the neighbor also confirmed this, along with the fact that they closed her in their car at night sometimes, with no litter box!).  Bri obviously favored us, she'd come to any of us that called, and begged for a scratch on the tummy, she ate our food, and played with our kids.  The neighbor said she wouldn't go to anyone, and when we told him she did come when we called, and even when we didn't, he said as far as he was conserned, she was ours.  Well, three or four days ago, i was leaving to pick up some groceries, and i saw that the neighbor's wife, son, and his wife were all outside, calling for "kitty" and looking around.  Strange, thought i, since up to this point they ignored her.  Maybe they were taking her to the vet or something?  I don't know, but i haven't seen her since, and i'm afraid the kids are coming very close to suspecting something.  I've been holding off their questions with "well, you know, sometimes she stays in the woods and doesn't come when we call" and "maybe she's napping somewhere."  Argh.  i'd at least like to talk to the neighbor about it, so i know to tell the kids that she went to live with someone else, or if she was sick or whatever.  i don't want to lie about something like this.  Ugh, if they did take her somewhere else, that was really mean, because they KNEW we were taking care of her, and would have kept her in a heartbeat.    i'm just not looking forward to whatever conversation is in the future on this one.