Does an adapter for a flat mount caliper to post mount fork exist? I have a CAAD12 disc which I'd like to fit SRAM Force 22 hydraulic to. I've been a bit enthusiastic buying things without really researching all the pitfalls of the different bits and bobs that go into disc brakes and compatibility thereof.

So, it turns out that the CAAD12 fork is post mount, but my calipers are flat mount. Is there an adapter to fit a flat mount caliper to a post mount fork?
From bikehugger.com


  What about fitting flat-mount calipers to post-mount framesets? Think again. No such adapters exist, and if I were you I wouldn’t hold my breath waiting for them to appear. It’s probably not geometrically possible.


Sounds like from that site that it's pretty much not even possible to get it working. Best option might be to sell your old calipers and get some new ones or see if anybody in your area is looking for a trade.