In northeast asia-mostly in China, but also sometimes in Japan and Korea-there is a tradition called the spirit marriage. It is done by placing a dead maiden’s hair and fingernails/toenails/both in a red envelope and throwing it away. Then, when someone picks it up, the person’s spirit is forever bonded with the dead maiden, as if they actually married the deceased.

It is not a common practice, let alone an encouraged one, but it is sometimes done to releave the deceased’s pain of having no partner in life.

That being said, OP said he got a red envelope by a mysterious woman. Although it’s not completely the same, I can see some resemblence here with the aforementioned tradition.

He was an unfortunate guy to have met the woman, but I think it is highly unlikely that she knew him. She is probably glad to have a new living, breathing husband ;)