Mo. Rev. Stat. § 532.050: Copy of warrant to accompany petition, when.

If the restraint or confinement is by virtue of any warrant, order or process, a copy thereof must accompany the petition, or it must appear, by affidavit annexed thereto, that by reason of the prisoner being removed or concealed before the application, a demand of such copy could not be made, or that such demand was made of the person by whom the prisoner is confined or restrained, and a copy refused.