WeChat has a feature named "message in a bottle". It functions much like you would expect; you can send a message to a random user or recieve one.

Your facebook page being restored after 20 years since you reached support.

Or that unread myspace mesage gets sent to you in a fishing scam.

maybe a message posted to an obscure usenet forum in 1996, bouncing around different servers eventually somehow surviving in google's archive to be discovered by someone randomly wandering around google groups...