What if I Was Putting Stake in What Was Being Written?

There was no sign that someone had written on it earlier and it had been like wiped off. I needed a prove to her what happened. As soon as it was fogged up again I went in there and it was like nothing had ever been written there. Those words are obviously from something else or some other time. Maybe it wasn't from the past. Maybe it was from the future. What was someone thinking when they wrote that? The fact that it said it worked makes me think is this something that was tested multiple times or somebody attempted to do it several times before it worked? If so how would they know that it worked?