Why did he say "v'Chikisi la'Shem"?
Rashi: Yeshayah says, I waited for Hashem, who hides His face from the 10 tribes. I wait for him to fulfill these words and save Beis David.
Rashi (18, from Bereishis Rabah 42:3): There was no harsher Nevu'ah for Yisrael than when Moshe said "v'Anochi Haster Astir Panai ba'Yom ha'Hu" (Devarim 31:18). That same day, He promised them "v'Ansah ha'Shirah ha'Zos Lefanav l'Ed Ki Lo Sishakach mi'Pi Zar'o" (ibid., 21).
Radak: This is a continuation of verse 16 (the Navi seals Torah with his Talmidim, and waits for Hashem).
Radak, based on Targum Yonasan: Verse 16 is Hashem's speech; here, the Navi says that he waited for Hashem, even when hides His face from Beis Yakov.
Why does it say "v'Kiveisi Lo"?
Radak: The matter is repeated in different words.
Malbim: Even when He hides His face from Beis Yakov, and abandons them to their enemies, I wait for Him - not one of His words will not be fulfilled.