Why is "recently added" playlist under iCloud control empty on iPhone?
You're not the only one suffering from this issue. A lot of people are complaining on the internet about this.  

A solution would be to turn off iTunes Match on your iPhone, delete all your music on your iPhone (it's all in the iCloud, right? So you won't lose any) and then activate iTunes Match on your iPhone. You'll be able to download all your play-lists, including the recently added.
This should do the trick.