Twiggy is a bit of a minx.
She got out on the first night through an open but stiff window and I thought Oh well !
When I went out to feed Henry she heard me calling and came bounding along the roof (my 'study' window opens up to roof over an extension).
So windows firmly closed....... except the little top one which i forgot about.
Just fed her and went downstairs came back up and she'd gone again. So opened all windows, managed to reach a dead mouse on top of the roof and in here scanning an article and she comes bounding back in!
Methinks she may have been coming and going all the time!!