Dissociative amnesia is a type of dissociative disorder that involves inability to recall important personal information that would not typically be lost with ordinary forgetting. It is usually caused by trauma or stress.

- Dissociative Amnesia - Psychiatric Disorders - Merck Manuals Professional Edition

But also with DID... alternate conscious states have an amnesiac barrier separating the full blown personality states.

Much different then being physically bonked in the head... we were emotionally, physically, mentally, spiritually bonked in our collective heads.