had forgotten, had never thought

[Mitsiboshu]

"I have forgotten" refers to the present.
"I had forgotten" refers to the past.

Today, it suddenly occurs to me. Once, I started to remember it. It should become past already. So, just like "I had never thought of it before", once you thought of it, it become past already.

I do not know, am I right?

 

[albertino]

"I have forgotten" refers to the present.
"I had forgotten" refers to the past.

Today, it suddenly occurs to me. Once, I started to remember it. It should become past already. So, just like "I had never thought of it before", once you thought of it, it become past already.

I do not know, am I right?

Perhaps, you've not understand the differences between the Present Perfect and Past Perfect yet.
"Have forgotten" is something (forgot) in the past but is relevant to something taken place at the time of speaking, i.e. relevance;
"Had forgotten" is a completed past action occurred before another past action, which has nothing to do with anything taken place at the time of speaking, i.e. irrelevance.
(Not a teacher)