Did the fish actually hit the fly? If they did and didn't stick, it's those damn Mustad 3407's! Next time you tie your popper, jam a doubled over piece of 25lb Maxima along the shank through a Gamakatsu #4 Octopus eye. Pull it tight to form a loop to loop connection with the hook eye.
If you are using the Dink Components, re-use the poppers. They're getting rare!