在宣告失踪和宣告死亡的语境中，负责暂时管理失踪人财产的人称为财产代管人。

在美式英语中，这个角色是conservator。

"If the missing person never signed a financial power of attorney, you may need to have a conservator appointed through the probate court in the missing person’s county of residence. Similar to a power of attorney, a conservatorship grants someone the authority to handle the financial and legal affairs of the missing person. In many states, a specified period of time must elapse before the court will appoint a conservator over a missing person."

发表在Duke Law Journal的Property Law: The Estates of Missing Persons中也表示，美国各个州法对这个角色有不同的称谓，最常见的是conservator和trustee。

"The individual appointed by the court to act for the absentee will be designated by one of the many titles used by the various states. Conservator and trustee are the most frequently employed names. E.g., CONN. GEN. STAT. ANN. § 45-87 (1960) (trustee); FLA. STAT. § 747.02 (1963) (conservator); GA. CODE ANN. § 113-2701 (1959) (conservator); N.J. STAT. ANN. § 3A:39-1 (1953) (trustee)."

其他文献中也有提及宣告失踪时的财产代管人制度。

"In some cases, family members may have reasons to believe that their long-term missing persons are still alive, even though they are nowhere to be found. In those cases, and if the persons left behind estates, conservators can take legal actions to manage the missing persons' properties."

遗憾的是，全国人大的英译本中并未使用conservator。

Custodian在不同语境中含义不同，例如在（1）管理未成年人财产，或（2）破产法语境中含义就不相同。但并不涉及宣告失踪和宣告死亡语境，参见这里。

It's wrong because you cannot separate English words from their context and use it in a totally different context in which it doesn't appear. In this case, conservator is the most frequently employed name in the context of missing person. Thus, it's unclear why custodian is used in the English translation of the Civil Code of the PRC. My best guess is that they didn't take an evidence-based approach. In the end, we have an incoherent English translation instead of a decent one.