I won't defend their actions in this specific case, but I will explain what's wrong with your logic -- the first thing you must do when you're not sure what's going on with a financial system you operate that handles other people's money is stop any assets from leaving your control.

Until they know for sure otherwise, someone could be trying to steal from you. Or you could be trying to steal from them. Or a whole bunch of other uncool things.

For some reason, the free association engine in my brain thought this story would teach this lesson, though I'm not sure exactly why I thought that. - http://thedailywtf.com/Articles/Special-Delivery.aspx