(TFS 173223:)
When a new member is added, the Member Id will be stored as a hashed value. The hashed value can be used as a variable when sending a link to landing page in a SMS (Variable=@HashedMemberId) A 3rd party can use the hashed value to look up the member with the new method GetMemberByHashedId in Member Service.
The hashed value will always represent the member Id, not any other identifiers like MobileNo or e-mail address.