I have the piece of paper with coloured squares on it but I don't know what I'm supposed to do with it to get a 3 digit code.

This happened on a repeat playthrough (trying to get all the collectables). Early in the game there is a box that has a magnet and a strange lock piece in it. I took the magnet first, and then was clicking around avoiding the lock piece checking to see if there was anything else in the box. Something I did closed the box and it was removed from both the scene and my inventory, leaving me with no way to get the lock piece required to continue....

So?

Did one HO without even one mistake, but it did not unlock. - I've started a new game and tried on the first HO in the game and got it now. Strange.

Hi. On a hospital gate location I combined stick with a band and instead of getting slingshot both elements disappeared and I'm left with nothing. Reloading the game doesn't fix this and I'm stuck on a level. I was enyoing the play but I don't think I want to waste time and replay the game again when I don't know if such thing will reproduce again....