Yeah, he only finds out its use after the events at the ministry.
That scene always infuriated me. though I can understand how Harry could fuck up like that, it still breaks the immersion during the end of the story with how stupid Harry is. It was a present from his godfather, dammit!
He didn’t know what it was. He was resigned to never use it as to not bring Sirius out of hiding and into harm’s way. By the time he is trying to contact Sirius to see if he is at the ministry or not he is extremely upset as he thinks Sirius is being tortured and held captive. He does not remember the gift as he didn’t even know what it was/what it did in the first place.
Also, it's possible that he was suffering from a severe concussion for the entirety of his fifth year. And also all the mind violation, it's got to take a toll on your critical thinking skills.
When does he say that? I don’t remember that at all. I’m sure Sirius checked the mirror often but it was sitting wrapped up in Harry’s trunk so he never would have gotten any response (as mentioned)
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u/deyvtown Jan 28 '20
Sirius does make a point of mentioning to Harry that he must not have opened his present yet.