I hate to disagree with Ethel but creating a trust is exceedingly simple - so simple that you can do it without realising it by eg the wrong wording in a will..
It's formally documenting it, getting that right and running the trust that are more complicated. It looks like it's that that hasn't been done.
If the trust was specified in a will, then that will is evidence of the existence of a trust. Not particularly safe evidence - it could be ignored with no one being much the wiser, at least until too late.
But no, there is no central registry.