In practice for more common fraud cases, we're seeing billions of dollars actually lost. Maybe the expense of retrieval would be higher than the value. Or it could be that the perps simply convert the money to cash, at which point it's gone. That's basically what happened to the $81 million fraudulently transferred from Bangladesh's account with the NY Fed:

https://www.nytimes.com/interactive/2018/05/03/magazine/mone...