How did he get on here ?

Back in September i found a screen name on my buddy list && I don't know how he got there so i iiMed him & Asked who it was he said Josh && He asked who i was && I told him...I asked where he lived he said Florida && I live in Rhode Island ...So i was all confused, so i said ' how'd you get my sn ? ' He said idk you were on my buddy list & I was like oh okay ? && I been talking to him sence , except through the month of October ...I started talking to him again in like Early November....Hes cool ....Oooh & He doesn't have a myspace or facebook so its not like he got my screen name off there...Well anyways is there a way i can find out how he got on my buddy list , im just curious.