A possibility for that type of damage could be that something (small grain of sand, seed, tiny rock, etc.) was on the keyboard area itself (on a key or even the frame between the keys) or the palm rest/trackpad when the lid was closed and caused an impact type of damage even though the impact would be minimal...more like a pressure impact. The tolerances are very small between the interior screen surface and the top case of the MacBook.
Regardless of what it was that caused this, take it in to Apple for an actual visual examination and determination for an outcome.