It didn't look like a weapon, it looked like a dumb shiny stone, and Hansel wasn't interested in picking up anything may or may not implode, poison or curse them. Of course the 'map' was practically a big blaring sign of 'things are not what they seem' so that was pocketed for good reason. "You mean the 'hey look, this place is evil' poster? Yeah, I have one."
The fact that in the centre of the pentagram there was the 'town hall' so to speak, just set off even more warning bells. "There's something else, I don't know what, but something. The Witch?" Although she'd never seemed to be able to turn herself invisible, and the heat was likely a little too homey for her anyway.