QPR Vs Cardiff

You got it spot on northwesthoop. Originally I thought it was a stone wall penalty, however,  I've now watched the game again and in retrospect  it was a very soft decision. 

It shows just how difficult the officials job is because my initial thought was that the Cardiff defender deliberately strong armed Armstrong. However, watching the replays from different angles not only wasn't it a penalty but the defender never deserved to be sent off.