I play this game often on a pad. There seems to be a "shelf" at the bottom under the collected items...

I play this game often on a pad. There seems to be a "shelf" at the bottom under the collected items. I cannot access this and need to wait until I use a bubble to collect the item in a three, towards the end of the game. If one of the bubbles goes down there I have no way of accessing it.

Any thoughts or help would be welcome?