Voter registration

I was able to vote in the last election but not without a slight snag. My name was still in the voters' list but when I was to cast my vote, my name was crossed out already in the list inside the precinct (not the one posted just outside). The chairman (I don't know her) was for a moment at a loss. I insisted that I be allowed to vote and she relented.

My question is, how does the COMELEC decide who should be struck out from the list and who decides? What are the criteria used? I have been abroad for over seven years now but I always make it a point to come home to Laguna at least three times a year. I am building my residence in Laguna and am planning of opening up my business very soon, right in the same barangay where I am a registered voter. I have vested interest in the future of Laguna and have as much the same right to vote as anybody who is staying in Laguna.