Hmm, the only advice I can give you is to look for it again :D
There's a spot/button you need to click in order to get the Achievement. This button is hidden in some menu. I've increased its visibility with the last update, so finding it is just a matter of time and stamina :D
About the Blessings, there's a upgrade called "Holy Vault" available at the Devotion Shop. What it does is increase your Favor Gain depending on the amount of Blessings you have. And more Favors mean more Gifts and in turn more Blessings.