It is not their fault someone stole their money, that is a basic principle of the legal system and ethics.
Perhaps of a good legal system with good honest people, however that is a chance in hell that even the devil would miss.
Although this discussion is rather pointless, considering an "IF" is at the start of the thread title, i will say that although it is not their personal fault that someone else took the money, how can you tell that that wasn't what they wanted?
Is it immediately assumed that its theft?
That is not rational, that is jumping to conclusions.
Only if the person files for lost money, is it theft.