Omg this happened to me with one of my cats where I used to live. I asked a neighbour to stop feeding him because he has so many allergies which was making him very unwell. For some reason this caused one heck of a spiteful reaction - she called a shelter several towns away to come trap him, claiming this cat was abandoned at her house when she moved in. The shelter just went ahead and took him, put him up for rehoming and never scanned his chip or contacted me. Luckily an independent vet happened to scan him and contacted me. The shelter were unapologetic and unwilling to bring him back or let me collect him. So they dumped him at this vets. I was lucky to get him back and we've since moved a long way away, but there's a rescue local to me now who keep leaving their traps around, despite people telling them who certain cats belong to. So when I see one, I destroy it now. I'm supporting several cases that are taking shelters to court at the moment. They present themselves as such martyrs too "We SAVE ANIMALS and WE DON'T GET PAID" etc, but in the same breath they become vulgar, rude, judgemental and tripping on their own power. I could bang on about it all night so I'll stop there, but I despise this new breed of animal "rescuers", cos they're making everything so much worse in the animal kingdom and for the people who genuinely love them.
I hope you get reunited with your cats. I'm unsure of the law in other places, but in the uk cats are currently classed as property. The police usually just tell you it's a civil matter and won't actually retrieve a cat that belongs to you. It's crazy, cos if it was like a bike that got stolen or a tv, they would seize it immediately and charge them for handling stolen goods. I hope you get answers and some solid support. You must be absolutely devastated right now, but please don't give up hope x