Adam Clarke on Psalms 74:9

We see not our signs - "They have taken away all our trophies, and have left us no memorial that God has been among us. Even thou thyself hast left us destitute of all those supernatural evidences that have so often convinced us that thou wert among us of a truth." But we may say that they were not totally destitute even of these. The preservation of Daniel in the lion's den, and of the three Hebrews in the fiery furnace; the metamorphosis of Nebuchadnezzar; the handwriting that appeared to Belshazzar; were all so many prodigies and evidences that God had not left them without proofs of his being and his regard.

There is no more any prophet - There was not one among them in that place that could tell them how long that captivity was yet to endure. But there were prophets in the captivity. Daniel was one; but his prophecies were confined to one place. Ezekiel was another, but he was among those captives who were by the river Chebar. They had not, as usual, prophets who went to and fro through the land, preaching repentance and remission of sins.