iOSFS mount vanished mysteriously

I know when but not why it occurred. iSH’s link to an outside directory suddenly unmounted itself in the space of a few invalid commands pasted to the cl, is dead without issuance of command, and isn’t reattaching like it had been since 1(68) when it was made persistent. The files on the iOS-side are still intact, along with the dummy directory on iSH’s side, but the inode-mount linking them is inop.