So Called "Remote Hack"

I would just like to note, some information may change as I find out new stuff. This is what I have so far.

What is "Remote Hack"?

Remote hack is the process of spamming a packet, or some information, to the server before the victim's client can, causing the server to think that the hacker IS the victim. In this case, unlike what every one else has said, it is the same packet that is sent when you double click your character. When they trade you, your character ID associated to your character is sent to the hacker. From there, he just edits the login packet to have your character ID in it, and tells you to CC. As you CC, s/he will spam that packet, and hopefully beat you to the server.
According to the information cheezwhizard gave me, it's most likely that the hacker will be on the same map and channel as you, as it makes things easier for them (timing wise, that is).

So, I've heard that each channel has a different server, and you change servers when you CC.

Who ever said that each channel has a different IP or "server", is wrong. Each channel has a different port (although, with the traffic Nexon gets, they typically allow 5 channels per server).

I think I was traded by a hacker. What should I do?

Log out. You can log RIGHT back in, too. Just log out immediately. No changing channels. No changing maps. Don't even go into the CS or MTS. Just log out. Why do I say this? As I said before, the hacker needs to spam the login packet as you change channels. Since the login packet is requesting the server to change you from channel x to channel y, you won't be sending that packet if you logged out, thus meaning that you are safe. Now, could the hacker still be spamming the packet as you log back in? It's possible, but they could have moved on by then. I'd give it a 30 minute waiting period before you log back in. What's 30 minutes when you can save your character?

Is there any other way of being attacked, rather than via trade?

Yes. As long as the hacker can grab your character ID, and can time your CC/MTS/CS attempt right, it can be done. So far, this is a few of the possible ways to get your character ID:
-Clicking on you to bring up Personal Info
-Trading you
-Inviting you to a Maple Messenger Chat
-Receiving a smega from you
There's more to add to the list, but those are just a few to show you that your character ID is everywhere, almost.
Going to bed for the night. I'll be back after school to continue answering more questions. Do read this guide though, as most questions asked are answered here.