Mo. Rev. Stat. § 456.037: Trust property — when deemed unclaimed.

1. Property of any kind remaining in a trust which is not subject to administration or distribution to or for an identifiable beneficiary may be deemed to be unclaimed property when the trustee, after reasonable and diligent search, is unable to find or ascertain the existence of any heirs, legal representatives, successors or assigns of any beneficiary to whom such property is distributable by the trust instrument, by any other instrument pertaining to the trust estate, or by the laws of Missouri.

2. Property of any kind remaining in a trust, which is distributable to or for the benefit of an identified beneficiary, may be deemed to be unclaimed when such beneficiary has, for three years after a good faith attempt to notify him in writing of his right to such property, failed or refused to claim the property.