Sometimes, when you start the game, close it, and re-open your world, it may be, that the two types of items (chests and signs) are missing, even if they are still there. That means that you can do everything normal with them, you only have to know where they are .
I put two screenshots on ther attachment, where you can see that the textures are missing, but you can read the text which is on the sign (TEXT).

Steps to reproduce:
1. Open a world.
2. Close the WHOLE game.
3. Re-open the world.
Then you should have it, if not, try again

And sorry for my bad English