Evilc

Can anyone help me please. I live in England. I have a front door and frame part of which comprises frosted double glazed glass. I have noticed marks of an x obviously hand drawn in some way on the glass. These cannot be removed by cleaning materials. They only show up at nightAt certain angles and against street lighting. I believe a local youth may be wanting to irritate me and is making the marks by way of a laser pen light or similar. Does anyone know whether frosted double glazed glass can be affected in this way? Many thanks