Can a cardiac mri miss scarring on the heart? is it possible to see scarring during an ep study but have a normal cardiac mri?

Yes; depends on size: The cardiac MRIs have inherent limits of resolution, so problems with anatomy below a certain size do not show up on the scans. The EP is a functional study - testing how the heart functions (electrically). While the EP doc gets a good idea of where the irritability is (based on position of the electrodes), it's primarily meant to capture & fix the electrical rhythm, not diagnose a myocardial scar