Background story: small office with ~20 people, a pretty girl saying in office chat room: "Hey, something strange. Someone put a small amount of money and this piece of paper with text in a pocket of my jacket. If someone do it by mistake or maybe he wanna to say something to me? Is it a flirting may be?"
No one response.
So I have some text on yellow paper, most likely an envelope, and want to know in which language this text is written and if text on it connected to this girl. After initial searches, I was guessing that it's Japanese characters, it looks like Hiragana or Katakana for me, but finally Japanese natives said that it's a most likely simplified Chinese and even guess that first char is 換.