Considering that the orders were rather sudden, some people might be traveling abroad, gathering herbs in the mountains, or engaging in seclusion cultivation, making them truly unreachable, but the Magic Sect still needs to report their whereabouts.
For example, if someone goes into the mountains to gather herbs, at minimum, we need to know which mountain they entered and with whom they made contact.
There's nothing much to this, it's equivalent to the sect conducting a comprehensive survey of disciple conditions.
However, the Hall of Sect Rules has decided that any disciple who remains unreachable will have a one-month grace period, and if they're still missing after that, they will be temporarily expelled.
Expulsion is a very severe punishment; according to Wuxia novels, it's equivalent to being expelled from the sect. This means the person will no longer receive the protection of the Magic Sect nor have access to its various cultivation resources.
