You probably got cookie grabbed. The way that works is you go to a persons UL and they have some coding that somehow takes a copy of all your cookies (which contains all your passwords and login info) and then the user uses that to log into your account and do as they please. To hack someones account, they would either have to hack your computer, or hack the Neopets servers which is like trying to hack into a bank server, that means they have to literally use a program to enter the server and take control over it to get the info (this is how a friend of mine explained it to me, so I dont know all the details, but if I can find the page on CGs in neopets again, then I will post it here).
TNT is really good about freezing stolen accounts, so thats no surprise there, but if you can prove, to their standards of course, that it is your account and it was really stolen, then they will give it back. But their standards are rather high.
Sorry they got stolen and iced, hopefully you have better luck in the future, I remember when my old account got unfairly iced and it was horrible, I was so furious, I even quit neo for about 2 years lol.
TNT is really good about freezing stolen accounts, so thats no surprise there, but if you can prove, to their standards of course, that it is your account and it was really stolen, then they will give it back. But their standards are rather high.
Sorry they got stolen and iced, hopefully you have better luck in the future, I remember when my old account got unfairly iced and it was horrible, I was so furious, I even quit neo for about 2 years lol.