Let me pose another viewpoint. If you walk out of the room you are in and close the door, can you still see inside the room? Part of the challenge is to be able to maneuver about in a virtual setting. I would tell them to make a map, or a set of rudders. This also allows you to change stuff to mess with them. Other solutions would be, allow them to make ONE mark at each turn using their paintbrush tool, (you can erase or change them if you want to toy with your victims um players), they can leave breadcrumbs, torches, coins, whatever, (and you can fiddle all of these things about a bit). I will also sometimes give them a map, (with errors) in advance.