You shouldn't have left in the first place, if you'd bothered to read the rules you'd know the risk of the situation given it states that grubs are raidable. Combat logging in any situation is inexcusable. If you get shot at, fight back. If you feel it was invalid, have a staff member look into it. Don't just leave on your own and expect good results.
I'm reducing your ban to two weeks from now, don't do this again.