There have been reports that items can be placed down in areas partially obscured by foreground walls, which means that when using touch controls it can be difficult to pick them back up.
If you find you cannot tap on an item to pick it up please try the following work around:
1. Tap on the book icon in the top left of the screen
2, Turn on 'Virtual Joystick'
3. Return to game and use your left thumb to move Ember next to the item and tap with your right thumb on the right of the screen to try and pick it up
Once you have moved the item you can turn Virtual Joystick off again and continue playing.