We've had lots of cats, several hated a collar and managed to get rid of them, so we don't bother now -- they are chipped of course.
For the OP (& others if in doubt), most female cats don't wander very far, so if you've got a real Houdini that's unlucky? Most of ours have retained excellent hearing, and even if turning a deaf ear to their name being called will zoom back on the rattle of a treat bag?
Oh, and we've never had a cat flap. We've had a couple of cats who - in their younger couple of years - liked to bring back little 'presents' (mouse, frog, etc) and if you've a flap they can bring them IN.
We once carelessly opened the back door for one of ours, and it was the one time she'd caught a mouse, (a very clumsy cat), she triumphantly dropped it in the kitchen, really pleased with herself and her present for us (it's how they see it). We spent 2 hours trying to trap the mouse as it scuttled under various cupboards and behind sofas, to the vast entertainment of the then 2 cats in residence.
There was a cat in the village, a dedicated wanderer, used to get in assorted houses, or on roofs, happily strolling around on his lengthy patrols. Another in a nearby town famously visits the local shopping centre, settles down on shelves or chairs until teatime! If you have a wanderer, it's luck of the draw, but they gradually do less as they get older . . .may not be much consolation?!