I didn't even know my character is wearing scarf until i noticed it. I tried to remove it in salon but the scarf does not appear in the salon. It is not even in my accessories list.

It's not a bug, I was wondering the same issue and figured it is just the alliance accessory. You turn it off at Community > Alliances Command > Equip Alliance Accessory > Do not Equip

It will always show up and take over your 4th accessory. So as long as you do what @RunawayXone suggested, you won't have it showing up.