I'm playing this on Playtiles. The game looks great, but I am stuck right at the start. I've found the "little etched stone, stuck in the rock", but I can't pick it up. When I go in the door 3 screens to the right it plays some music, but all I can do here is look at the sign (that appears to be missing a rune). I assumed I'd pick up a rune to open the door, but I can't actually pick one up anywhere. Am I being stupid?