I was playing my Soul Silver version for the second time after transferring my pokemon to pokemon White version, and when I got to the red Gyarados, I decided to defeat it, as I already had one. Shortly after, I stepped in to the grass to the right of Mahogany town, and the first step I took, I found a shiny Spearow. Did defeating the red Gyarados cause that, or am I just really lucky?