ותאמר ציון עזבני ה' ואדנ' שכחני (ישעי' מט-יד)
The Haftorah of "ותאמר ציון עזבני ה'" describes the feeling of hopelessness and abandonment felt by Klal Yisroel in the aftermath of the devastating Churban. Yeshaya HaNavi says; “Tzion [Klal Yisroel] said, Hashem has forsaken me, and Hashem has forgotten me.” If Hashem had forsaken the Nation, then surely He had forgotten the Jews as well! Plus, when the Navi uses the word "עזבני" - abandonment, he juxtaposes it with Hashem’s special four-letter ineffable Name; but when he uses the word "שכחני" - forgetting, Yeshaya uses Hashem’s name of mastery - “Adnus.” Why?
R’ Levi Yitzchok M’Berditchev zt”l (Kedushas Levi) explains that the term “abandonment” applies to one whose affinity to a person or thing from the start was unconnected to any favor done for them and now no longer recalls their original kinship. On the other hand, "שכחני" - forgetting, is applicable to one who received a favor but does not recall what was done. The Name of Hashem has no relatable characteristic and is thus connected to the term of abandonment since Hashem’s affinity for Klal Yisroel is purely out of His love for us. However, His Name of mastery indicates the attribute of kingship which comes through the Jewish people who accepted the Torah and His Kingship upon themselves, because there is no king without a people. So, it is separate. Klal Yisroel cried about the perceived abandonment of Hashem’s unchangeable love, as well as the seeming forgetfulness of them even though they accepted Hashem’s Torah and His Kingship.