If your divorce has been finalized then you may be able to send the 401(k) trustee a copy of the QDRO and request information. Otherwise, it is highly unlikely that the trustee or administrator will share any information with you as it is considered confidential.
Do not delay on the QDRO as it is possible for your former spouse to remarry or request a distribution, which will complicate matters. Contact a fee-only advisor for assistance...
The other side would be smart not to make a big deal about this... if you get lawyers involved it will just cost you more out of pocket. This should have been discussed int he final terms of your divorce and a QDRO most likely will be needed by the institution that holds the 401k money.