Am I missing something or have they completely vanished?
No, Duolingo started playing hide-and-seek with you. On the left side of your skill tree, there is a 'weekly progress' tab. If you click it, you get the coins.
Ah thank you. Being able to keep track of my achievements with them is a nice little incentive.
It would be better if it defaulted to our weekly progress. I more interested in knowing what I doing now than the cumulative total.