Well, it turns out I was right, previous owners got hold of her
They used to live in the same little group of flats I do and she kept disappearing then just never came back one day (We'll skim over the not looking for her bit). Then they moved last week but were coming back to feed a rabbit they had until they could rehome it (we'll skim over that too). She said they had to move because their flat was riddled with damp which I can understand. Turns out the black cat that visits me is also theirs and has stayed with a neighbour here as she likes to get out and wasn't happy being kept in.
So they managed to grab her the day she went missing obviously and have now taken her to their new flat. Apparently they have a 6 month old puppy who is not used to cats and keeps chasing her
But otherwise they've said she is happy and not asking to go out. I've told her that if she has any problems etc then to just get in touch with me and I'm happy to give advice or have her back.
On the positive side she said that they'd taken Little Miss off her mum and first thing they did was get her spayed
So she's at least a little bit responsible. She also sounded really really young (or stupid, you take your pick) but I am grateful she took the time to get touch and let me know she was okay and she asked after Dave too.
So a sort of happy ending, just not for me and Dave (I'm back to not getting a lie in anymore, Dave has decided I can be harassed for breakfast again now he doesn't have a friend to play with).