That theory is simple. Holding velocity constant, the more money you print, or in this case any time the government engages in open market operations, or loosens monitary policy, the less the dollar becomes worth. Inflation rises.
Now, note that I said we are holding velocity constant. Its a given that we have printed a fuck ton of money. The reason inflation isn't kicking in is because velocity is low. Velocity is the amount of times a dollar changes hands in a given period of time. If velocity increases to pre recession levels, then we will see the full effects of inflation and all this money we printed.