Hi there. My daughter is 2 1/2 and this sounds sssooooooooo familiar. I think in addition to the vacation that changed his routine, he may well be in another independence development stage.
The first thing I recommend is to embrace the expectation that you won't stop the behavior completely. They're going to go through their "stuff" in their own way. However, we can sure help reduce it.
I found that when they act out negatively, they are trying to get 1) attention and/or sense of significance, and 2) power. When I supply both of these (which I had to learn in short order or I'd have started drinking wine until the pain went away

), I found the behavior reduced significantly.
I guess one thing we don't know here is your daily routine. Does he go to daycare or have a nanny, or are you home all the time? I work part time and the kids go to an in-home daycare twice a week. Those are the days that were the worst behavior wise. I learned that my daughter really just needed some alone time with me to connect each day. I got her up just a little earlier than I'd been doing (less rushing and "hurry up"). We'd snuggle in her bed and talk about the day. She was much better at getting up. I did this again when I picked her up from daycare, I got down on my knees and had her show me her art project, talk about what she did, have hugs, etc. for about 3-5 minutes before we left. Then a little more when we got home. The evenings got better. This is how I provide her need for attention proactively. When they're acting out, they need it even more, believe it or not.
For significance, she has some small chores she does. She has to take off her shoes when she comes in and her job is to feed the cats. We lay on the recognition when she does it, "Thank you for feeding the cats. They really appreciate it and so do we. See how they're happy to see you?" She beams and is now doing it without reminders or even recognition after. The cats getting excited when they see her is what makes her want to do it, I think.
For power, we offer lots of choices. "Do you want this or that?" or "You can have this or that." I've also found she gets more cooperative when I ask her what she's supposed to do rather than tell her. This was a real gem: She was refusing to wash her hands before dinner. Instead of nagging, I asked her, "What do we do before dinner?" She eventually realized, "Wash hands!" I excitedly say, "Yes, you're right!" At first I had to ask if she wanted me to join her or not, but soon she started running in and doing it herself. She had the power now, which made her want to do it rather than struggle with me over it.
So with all that background (hope you're still with me), I'd recommend giving your little guy a little more attention. It sounds like he's needing it right now. Undivided, no siblings, no phone attention for a little bit each day. Have him call the shots on what you're doing. Basically, fill his "love cup" if you will.
When he's acting out and throws a toy, ask what happens when he throws the toy. If he says no, or anything other than the right answer, you tell him calmly, "the toy goes away" then take it. Then talk to him, "I know you're upset that the toy went away, but I have faith you'll not throw it next time. What can we play with now? I'll play with you for five minutes, so do you want to play with the car or train?"
It doesn't work the first time, remember. You just keep trying and in time he'll feel you're responding to his needs.
Wow, this got long. Hope this helps. I write about this stuff on my blog so I got a bit carried away. Good luck!
Jen (aka Heligirl)