Key Not Appearing in Game

[Romulator]

I think that by in game modelling, the small chest entity will cover up a key when it is placed along the 0.25 scale. If you can locate your key in the Level Editor, click it and move it up the Y axis by a little (about 0.1 should be alright), which will raise it up a bit. Gravity in game will cause it to fall down to the bottom of the chest.

If it is NOT that, then I can assume that there is something wrong with the mesh (the texture of the key). Have you got a Steam or Retail version?