Your trust should permit the use of a copy of the trust. I put that in all of my trusts, however, I am very careful to control the distribution of copies.
If you know the lawyer who wrote your trust, he or she should have the trust either as a copy on his computer or a signed copy. I keep both a signed copy and a scanned copy so that there is little chance that the trust is completely lost. If you have used your trust in transactions with financial advisors or investment companies, perhaps you provided them a copy or at least a certificate of trust. All investment companies will accept either of these documents, so one of them may have a copy of yours. And really make sure they look, some people have the knee jerk reaction of saying I don't have the document when they in fact do have the document. If you have lost the trust and the information about who wrote the trust, you may want to ask any professional who may have seen the document, these could be life agents, investment advisers, charities, doctors, other family members, and the person who you named as trustee. Don't let being embarrassed stop you from asking. Trusts, wills and other documents, spend almost their entire existence being out of sight, therefore, out of mind and very easy to missplace. If you have lost the trust you are not alone.
Ask everybody who may have seen the trust to contact each of the attorneys he or she has worked with since they started working with you and ask those attorneys if they recall writing a trust for you. Most agents with any brokerage work with a limited number of attorneys so at most the professionals you ask will have to call or write to 2 to 10 attorneys at most. Also because agents make their money through networking ask the agent to go through all of his business cards, your attorney's card might just be there. Additionally you probably at least remember the age, gender, etc. of the attorney; call around and see if you can't find him yourself. Since we don't change that much as we grow up you are likely now to choose an attorney in the same manner you chose before. Would you only do business with small firms, like the lawyer to be older, and a woman? Get your criteria together and than find lawyers who match it and call them and ask. You could also ask every lawyer in your area. Write a short simple letter that says, I am (name); I had a trust drafted 5, 10, 15 years ago; this is the name of the trust, and did you write it. Unless the attorney has retired (if it was a firm and not a solo the firm may still exist and have a copy, even if the lawyer is retired.) I have been writing trusts for twenty years and I can check by name, every person I have written a trust for. Too find a lost trust you will have a good amount of work to do, but if you do it, you have a fairly good chance of finding your old attorney and with him or her; your documents. If you cannot find the lost trust you will need to bite the bullet and have a new attorney write a revocation of the lost trust, provided you were the grantor of the lost trust, or a restatement that replaces the old trust with the new. To do that you will absolutely need the services of an experienced trust attorney.