“Nobody forgot the holocaust.”
"The nature of severe trauma is that people have trouble forgetting. I never heard of someone who was in Auschwitz, Dachau, whose experience was so bad they couldn't remember it. The nature of trauma is that you can't forget.” - Joseph Deltito, in the FMSF Newsletter. 
“We have been asked to believe that the recovered memories of abuse were repressed as a defense against the trauma… We ask in return why we have never heard stories of repressed memories from survivors of the Holocaust? This is an acknowledged historical event of almost unequaled horror that included rapes and torture. Why no stories of repressed memories?” - FMS Foundation Staff, in the FMSF Newsletter. 
In actuality, many survivors forgot the holocaust - this blog post [link] lists 22 resources that provide compelling scientific evidence in support of the phenomena of dissociation and recovered memory in Holocaust survivors. These are a few notable examples:
Durlacher, G. L. (1991). De zoektocht [The search]. Amsterdam: Meulenhoff.
Dutch sociologist Durlacher, a survivor of Birkenau, describes his search for and meetings with another 20 child survivors from this camp. Excerpt: “Misha…looks helplessly at me and admits hesitantly that the period in the camps is wiped out from his brain….With each question regarding the period between December 12, 1942 till May 7, 1945, he admits while feeling embarrassed that he cannot remember anything….Jindra…had to admit that he remembers almost nothing from his years in the camps….From the winter months of 1944 until just before the liberation in April 1945, only two words stayed with him: Dora and Nordhausen….In a flash I understand his amnesia, and shocked, I hold my tongue. Dora was the hell which almost nobody survived, was it not? Underground, without fresh air or daylight, Hitler’s secret weapon of destruction, the V-2 rocket, was made by prisoners. Only the dying or the dead came above the ground, and Kapos, and guards.” 
Jaffe, R. (1968). Dissociative phenomena in former concentration camp inmates.
Case descriptions include amnesia for traumatic events and subsequent twilight states in which events would be relived without conscious awareness. Excerpt: “The dissociative phenomena described here turn out not to be rare, once one is on the look out for them.” 
Kuch, K., & Cox, B. J. (1992). Symptoms of PTSD in 124 survivors of the Holocaust.
Potential subjects with confirmed or suspected organicity, bipolar or obsessive compulsive disorder were excluded. One group (N=78) had been detained in various concentration camps for greater than 1 month. A second group (N=20) had been detained in Auschwitz and had been tattooed. A third group (N=45) had not been in labor camps, ghettos, or had hidden in the illegal underground. Psychogenic amnesia was found in 3.2% of the total sample, in 3.8 of the general concentration camp survivors, and in 10% of tattooed survivors of Auschwitz. 17.7% (N=22) of the total sample had received psychotherapy. The tattooed survivors had a higher number of PTSD symptoms overall. 
Moskovitz, S., & Krell, R. (1990). Child survivors of the Holocaust: Psychological adaptations to survival.
Excerpt: “Whatever the memories, much is repressed as too fearful for recall, or suppressed by well-meaning caretakers wishing the child to forget. Without confronting the fear and recapturing the fragments of memory, the survivor cannot make the necessary connections which allow reintegration of their whole life; neither can they obtain the peace of mind that comes with closure.” 
Stein, A. (1994). Hidden children: Forgotten survivors of the Holocaust.
A collection of interviews with child survivors who were hidden during the war. Excerpt: “Over the years I have been trying to re-experience those feelings, but they kept eluding me. I was cut off from most of my memories, and from relieving the anxiety of that time….I remember nothing about the time I spent with those people…not a face, not a voice, not a piece of furniture. As if the time I spent there had been a time out of my life….What is missing? Why can’t I conjure up those memories? I am staring into the darkness with occasional flashes of light allowing me to unearth bits and pieces of life.” 
 Mikkilineni, Rupa (Producer). (2005, August 17). Nancy Grace [Television broadcast]. CNN.
 FMS Foundation Staff. (1992, July). Repressed Memories. FMS Foundation Newsletter. 1(7), 3.
 Durlacher, G. L. (1991). De zoektocht [The search]. Amsterdam: Meulenhoff.
 Jaffe, R. (1968). Dissociative phenomena in former concentration camp inmates. The International Journal of Psychoanalysis, 49(2), 310-312.
 Kuch, K., & Cox, B. J. (1992). Symptoms of PTSD in 124 survivors of the Holocaust. American Journal of Psychiatry, 149, 337-340.
 Moskovitz, S., & Krell, R. (1990). Child survivors of the Holocaust: Psychological adaptations to survival. Israel Journal of Psychiatry and Related Services, 27(2), 81-91.
 Stein, A. (1994). Hidden children: Forgotten survivors of the Holocaust. Harmondsworth, Middlesex: Penguin Books.