As some others have mentioned, the picked state needs to be a bit more clear.
Some suggestions -
1. As a border around 'Pick' to indicate it as an action
2. Once an item is picked, add a mask on the whole page, with only the picked item in front of the mask. (This is going to be a bit challenging, I'm guessing, to show the gaps between the items as you scroll)
3. Once an item is picked, the 'Cancel' and 'Place' bar should have a background. Sometimes this overlaps the list and is not clearly visible.
4. It should not be possible to scroll way above or below the list.
5. On 'Cancel' scroll back to the item.
Again, congratulations! It's one thing to think of something, quite another to be able to implement it nicely.