Thanks, all! I am sure when the time is right, the right cat will cross my path.
I think my male cat Mowlie is missing her. They had been sparring partners for 14 years on a near daily basis. He was never aggressive, just liked a bit of a rumble, I think! He's been sitting quietly and staring around at times. When I brought the empty carrier home, he sat peering in it for ages, then sat back as if he was thinking 'I saw her leave in that, but she's not there now, so where is she?'