If you really had manually saved that Pages document beforehand, then Pages autosave would be saving your document about every 5 - 10 seconds if there were changes to the document. If you closed the document, the last changes would be in the document. If you had not manually saved the document once, then autosave would not be enabled, and closing the document would be a finality of lost work.
Some non-Apple cloud services and filesystems do not support Apple's autosave feature and it would present a dialog to that effect.
You should be using an external Time Machine backup that runs every hour. It is the preferred means to retrieve Pages documents that were saved at least once. Without Time Machine, you might try opening the document and from the File menu > Revert To > Browse all versions. Then use the arrow keys to go back in time until you (might) see your lost work. Then restore.