Have you made a police report yet?

The problem with tracing Bitcoin transactions is that there is no obvious link and that the point where the funds were deposited into the exchange can very well be after the keys/Bitcoins have been sufficiently washed and passed around. There wouldn't be any incriminating evidence to freeze those funds. Exchanges are not known to be very cooperative with divulging their customer's identity without sufficient evidence to the authorities.

If you're aware that it has gone to an exchange, then you can provide it to the authorities and that is about it. No tracing services would be able to do much more than that.