Hello, sorry to hear that. Seems I made the same idiotic mistake a while ago XD. There is this jerk who creates toons, sometimes very similar to our friends, and impersonate as our friends to scam newbies out of items. Basically he tricked me into thinking he was an account of a real life friend of mines and told me to transfer my staff over to them to upgrade it and said they would give it back after upgrading. This was I believe in my first 1 or 2 months of lineage 2 and had very little understanding of the game. Needless to say, NCSOFT didn't restore my items, but it's not their fault though, they can only restore stuff under very narrow circumstances. It's bloody scammers who take advantage of other player's naivety and trust. What IS important is whether NCSOFT takes actions against scammers, and ban them. And to the best of my knowledge, they do. Though it's more difficult than one may think. Since they may use ways to hide away IPs, etc.
Regardless, even though I was a victim of this jerk, you can take lessons from it: Don't trade over things to other players. If they are going to help you, they will tell you how to do it. I think someone on this forum revealed who this looser is, though the post was removed due to it legally considered doxxing. I only lost around 70b, could have been worse.
Best of luck!