It's not untraceable, just pseudonymous. In fact, it's easier to trace where it went, but harder to tell who has it.
Imagine your bank. If you transfer money from your account to your friend's account, I cannot see that you have done this. That transaction is private. However, the banks know exactly who you and your friend are because both of you were required to submit identification when you opened the accounts. The transfer is identified. Bitcoin reverses both aspects. You can open as many accounts as you want without identification of who you are, but any transfers can be viewed by anybody.
Therefore, if we know where the money came from, we can see where it was transferred to. In turn, we can see anybody they pay. What we can't easily do is figure out who controls those opaque addresses without investigation of other things. The question is whether we can identify the criminals before they convert their public asset into something private. If we can stop them converting, they effectively lose control of the money because they can't spend it. If they're fast at laundering it, then they have now pulled off an unidentified and private transaction and can proceed to hide their new wealth.