What does the phrase 落し物をされる mean in this sentence? It doesn't sound like correct passive voice


The context is that someone has lost a present and the main character goes to
look for it. He goes up to a shopkeeper who asks him what's wrong and he
responds with

> ええ、少々探し物を。昨日チャミーさんが **落し物をされたらしくて** 。。。何か気づかれませんでしたか？

This looks like the passive form. I'm confused because if Mrs. Chammy is the
subject here, then what is being done to her and who is doing it?

