Amnestic

loss of a large block of interrelated memories; complete or partial loss of memory caused by brain injury, shock, etc.
Contemporary Examples

Key actions: Thinking fond, amnestic thoughts about the last snow day.
So You Are Enduring a Temporarily Paralyzing Winter Storm Kelly Williams Brown February 14, 2014

noun
a defect in memory, esp one resulting from pathological cause, such as brain damage or hysteria
adj.

“causing loss of memory,” 1879, from Greek amnestia “oblivion, forgetfulness;” see amnesia.
n.

“loss of memory,” 1786 (as a Greek word in English from 1670s), Modern Latin, coined from Greek amnesia “forgetfulness,” from a-, privative prefix, “not” (see a- (3)) + mimneskesthai “to recall, cause to remember,” a reduplicated form related to Greek mnemnon “mindful,” mneme “memory,” mnasthai “to remember;” from PIE root *men- “to think, remember” (see mind (n.)).

amnestic am·nes·tic (ām-něs’tĭk)
adj.
Amnesic. n.
An agent that causes amnesia.

amnesia am·ne·sia (ām-nē’zhə)
n.
The loss or impairment of memory.
amnesia
(ām-nē’zhə)
Partial or total loss of memory, usually caused by brain injury or shock.
amnesia [(am-nee-zhuh)]

A loss of memory, especially one brought on by some distressing or shocking experience.

Note: A common variant is selective amnesia; the term is applied to public officials who, when questioned about alleged wrongdoing, profess that they cannot remember.