Hi everyone, my first post here so forgive me if in wrong section

I picked up my Astra H SRI 1.8 Ext. pack this week, its only done 17k and is like new. And I love it!

But when I gave it its first wash one of the headlight misted up really bad, so I took it back to vauxhall.. who told its not covered by the warranty as its a known fault? said to drive round with the lights on to dry it out.

Is this true? not very happy about it to honest