Go to living room. Look close at the wooden box right of the bedroom door. Use the ornament from locker room on box. Take the key. Go to the orange locked cash box in the bedroom. Use the key just taken on cash box. Open and look close at coin with 3842 written on it.

I usually save at every new location, just in case.

That is what I do too - no matter how engrossing the game is.

I think Mikael told me about this. I will check, but is it possible you might have slipped on the mouse and clicked back at the same time? I know he said that there was a bug and it might have been at that place. Hang on and I'll send him here ...

I have spoken to him now, and it is a bug at that exact spot. It happens when you click on back I think when you try to open the box. The only thing you can do is to go back to your nearest save. It's a hard bug to find since it probably happens by accident. I have beta-tested it lots of times but never noticed it. Hope you have a good save to go back to.

(oops, should've edited my post instead of posting again. thanks for the fix )

I have the same problem!
Too bad my last save was rather far away - still, some chance to look at all the beautiful pictures one extra time