Close friend flew through their recently and had security claim see through bag for toiletries wasn't self sealing, they had tied it and was refusing to allow it go through BUT would sell them a bag for a pound and rapidly produced a bag from their pocket.
Security member was asked "Oh so you sell them then can I have a receipt" at which point he suggested on this occasion they would allow it go through.
Of course it may be a one off with security member just happening to have a bag in his pocket.