Something weird just happened.

I was doing Hero mode with my special "tool". (I did set it to private dungeon)
After I finished the quest and went back to Colhen, a guy showed up.
He said: "Hey, how come you only have twin spears on you?"
I said: "Nah..Its only Kalis"
He said: "Really, even hero mode Kalis, you are the hacker right?"
I was like " HOLLY SHIT, how did he know .."
He even said, He knew that I spent lots of time in Rocheste and He wanted me to give him some mats that I farmed.
All this just creeps me out..
I think I should keep low profile for a while..

If you set it to private, then no one can see the boat. He was probably just assuming you were a hacker because most people never use basic weapons even when doing easy runs (it becomes stupidly slow then). If you must, equip your high-level weapons when in town and dock, then once you're on the boat switch to basic weapon.

Two more tips:
Always find an empty channel before making a boat.
Select Replay Dungeon rather than Return to Town after finishing.