They need to file a police report, and get in touch with their bank. It's likely the money has already been transferred to a different bank, but the corresponding bank might still be able to freeze the account if it is still sitting there.

Then again, it might be transferred again as well. Money is hard to trace if it moves through different jurisdictions, as every country has different banking and privacy laws. Your client might very well hit a dead end for such a (in the grand scheme of things) small amount of money.