I was also wondering. The reason is that he left Sweden and apparently moved around quite a bit. He is reported to have been residing mostly in Berlin and his girl-friend lived in Gdansk, Poland.
[edit: addition] The reports are ambiguous; it sounds like what they mean is: the Swedish police collaborated with the Polish police to track him down.
[edit: addition] The reports are ambiguous; it sounds like what they mean is: the Swedish police collaborated with the Polish police to track him down.
Source (in Swedish): http://www.expressen.se/kvallsposten/pirate-bay-grundaren-gr...