If your mother can't find it, there's no way to find out who prepared it - unless she has real estate and the lawyer who prepared the trust transferred the real estate into the trust. Usually, if the lawyer prepares the new deed, there's a notation in the upper left hand corner that says "recording requested by" and lists the lawyer's name.
You might also see who notarized the deed; usually the notary works for the lawyer who prepared the trust.
My only other idea would be to check your mother's checkbook register for the time period when the trust was prepared ... maybe she can find out who she paid.
The information you obtain at this site is not, nor is it intended to be, legal advice. You should consult an attorney for individual advice regarding your own situation.
My only other suggestion would be check with any other institution that is holding assets in the name of the trust, such as a bank or brokerage house. They would have required some documentation from your mother in order to fund that particular account into her trust, and may have kept a copy of that documentation in their files. If they did, the name of the drafting attorney should be in there.
I wouldn't mess around with this too much. If she forgot who prepared the trust, there's a pretty good chance that it was prepared long ago--and needs updating. Even if she found a copy, there could be some problemes as most institutions want to see the original copy. It's probably a good idea to prepare a new trust. Make sure to include a clause revoking all previous trusts.
