A couple places to look for some clues:
- If the trust was a revocable trust, then there is probably a stock investment account, or bank account statements. Those would be addressed to the trustee. Trustee should have a copy of the trust.
- Those same accounts, would undoubtedly have generated taxable events in prior years, to which there would be dividends or interest. Look in copies of prior taxes, and the backup documents for the taxes, for an idea of where the assets were being held, and who the trustee was.
- If it was an irrevocable trust, then there would be a totally separate tax form, which your dad may or may not have a copy of. He also may or may not have been given copies of account statements. Those may give you an indication of who the trustee was.
- Contact family lawyer.
- Sometimes investment houses, will require a copy of the trust when they open the account. They may or may not have a copy. If they did, it would be unlikely they give you a copy out of the blue, so may require letter from lawyer so request looks official (in some manner).
- Safe, or safety deposit boxes should have a copy. Check where he banks to find out if had sdb, would need probate and lawyer to get access if not already on signature card.
- Check on data DVD's, CD's, computer harddrives, and potentially backup services for softcopy files.
- Give some college kid hacker couple hundred bucks (only kidding).