Prayer is relevant when making requests regarding the future. Requests for changing past occurrences are prayers in vain.

Concerning one who cries out over the past, this is a prayer in vain. How so? If one’s wife was pregnant and he says: May it be God’s will that my wife will give birth to a male child, this is a prayer in vain. Or if one was coming on the path home and he heard the sound of a scream in the city, and he says: May it be God’s will that this scream will not be from the members of my household, this is a prayer in vain. (Mishna Berakhot 9:3)