Does My Cat Feel Abandoned When I Leave for Vacation?
I literally just posted the same thing about dogs, and had so many requests for cats. So, to all my feline-owning friends, especially my in-law, Frannie, here ya go!

Just look at that puss! Mikey is giving his mom Frannie some serious side-eye.
Well, to answer this question, we have to fast forward to our return. Have you ever noticed that your cat acts a little strangely upon your arrival back on home turf? Maybe they greet you, but are aloof. (Cats? Aloof?!) Or maybe they lurk on top of a cabinet, looking like they're positively bored by your mere existence, much less your warm reunion.
What's happened to Fifi!?!?
Experts say, they're just doing what cat's do. Certainly some cats take separation hard. They may even act out while you're away. More likely, your trip to London has disrupted their world. Felines like schedules. And your trip was not on their schedule. If 'acting out' means they're showing some aggression, it's very likely they're sensing unsettling new smells that you've brought home. And believe it or not, that may turn them into dastardly fiends, at least till they start smelling the old, familiar YOU scent. That's because cats identify with humans based on smell.
"Who is that tall, blonde lady? She looks like Pet Set Juliet. She acts like Pet Set Juliet. She even sounds like Pet Set Juliet. But she smells...off!"
Crying, meowing excessively, not eating - all heartbreaking to witness, but completely normal. So what to do? Some pros say definitely do not smother them with attention. It'll only put them off, or worse, piss them off. Let your cranky cat come to you. Remember, he's not sure it is you, not yet at least.
Another trick o' the trade: treats. A smart furbaby owner will have them in hand the moment you walk in your house. And if they're being aggressive, as always, do not reward them!

There are also steps you can take prior to vacay that'll reduce the likelihood of an unpleasant reunion. Vets recommend calming sprays like the Amazon smash-hit FELIWAY CLASSIC diffuser and treats that reduce anxiety.
Another great idea (I mean, fantastic, frankly) is to make sure they have a pet sitter, and they're comfortable with her. A reliable, first-time pet sitter should be happy to visit with the cat free of charge for a few minutes, once or twice, to establish a relationship with Fifi. And if you already have a pet sitter, even better having them stay at your home overnights, so Fifi feels a little more of that familiar structure.
I know quite a few people (Hi FRANNIE!) who are hesitant to even take vacations because of fear their pet will feel abandoned. This is a reasonable feeling...for a human. But dogs and cats are not humans; their physiology, minds, emotions are quite different from ours. The key is leaving them in the company of someone they already know, trust and like. (NOW, LET'S BOOK THAT TRIP TO ITALY, FRANNIE! MIKEY WILL BE FINE!)

Listen to Pet Set Juliet, mom!