Icecrown raid lockout issue (?)

So I joined a VoA 25 raid as the last, 25th person.

Once I arrived to the boss and started buffing, the leader started a discussion whether PvP should be a free roll or MS > OS.

I did not agree with the decision, said I am going to leave on /raid and i left before the fight even started.

I left the group, fight started when I was HSing and after a couple of minutes I got a notification "You are now saved…" when I was in Dalaran.

Why am I saved if I haven't participated in the fight, left the group before the encounter started? Are these some kind of anti-ninja measures? In this case did I do something wrong, did I break any rules?