In Frankenstein, where are the monster's feelings of abandonment mentioned in the book specifically?
In Volume II, Chapter II of Frankenstein, the creature first comes into contact with Victor since his "birth." The Creature does not face a very warm welcome from Victor (given Victor believes him to be responsible for the deaths of both William and Justine).
It is in this chapter that the Creature first states his feelings of abandonment.
“I expected this reception,” said the dæmon. “All men hate the wretched; how, then, must I be hated, who am miserable beyond all living things! Yet you, my creator, detest and spurn me, thy creature, to whom thou art bound by ties only dissoluble by the annihilation of one of us."
Through the Creature's stating of Victor's shunning of the creature, the Creature recognizes Victor's abandonment.
Later, in chapter three (Volume II), the Creature states that when he first became aware of his surroundings, he felt he was a "poor, helpless, miserable wretch." It is at this point that the Creature first begins to weep. The Creature surely feels abandoned given he is alone.