In this level, you'll have to push down on a button in the north-west corner of the level to activate two extra platforms. When you eventually make it over the other side, you will be forced to push down on a switch which will set off a rolling boulder. Immediately turn around and keep walking back through the path until you can move away, and re-enter that area to find the Key at the end. Then use the boulder to reach the raised pillar. Follow the path around to find Ricky.