The phrase "have been thrown on" is a way of saying that Yahweh has taken care of him as if Yahweh had adopted him as his own child. This can be stated in active form. Alternate translation: "It was as though you had adopted me right when I was born" (See: [[rc://en/ta/man/translate/figs-idiom]] and [[rc://en/ta/man/translate/figs-activepassive]])
This implies that Yahweh has always taken care of the writer. Alternate translation: "you, God, have taken care of me" (See: [[rc://en/ta/man/translate/figs-explicit]])