I had been looking for a new career, and recently became very interested in learning all there is to know about repairing and modifying smartphones and tablets from watching videos on how to repair my own smartphones. I am also interested in performance customization and would like to learn more.
It could be that one of the connectors to the LCD came loose. You could check that first. If it isn't that, to make 100% sure that it is NOT the digitizer (which is located directly beneath the screen), you could hook it up to another working Note 3 and test it. The other possibility could be the motherboard. The motherboard is a little less costly to replace, especially if you were to find a secondhand one. If you DO decide to buy a brand new digitizer, you can find them for about $130-150 if you shop around. I would NOT pay $250!