Answer:
The man looked quickly and saw a flag.
Step-by-step explanation:
To glance means to take a brief and quick look at something. As the line says that man “glanced”, this means he quickly looked. “The old flag met his sight” means that when he took that quick look, he saw the flag.
He did not look at it carefully or for a long time as the line does not suggest that and that is not the meaning of the word. There is also nothing to suggest it was hidden and couldn’t be seen.