This is an on-going problem even for such simple matters as contact 'phone numbers / email addresses (or physical addresses!).
In this technological day & age, there has to be a simple way to send / receive an e-TG21 to / from parents / guardians so that the information flow is quick / accurate. Or, an e-acknowledgement of an event - "I confirm that I give full permission for Cadet Bloggs to do whatever, at wherever, emergency contact details are XXXXXX & that there are no new medical conditions to affect."
Of course, that is treating the symptom, not the cause - work on a methodology to eradicate the bloomin' thing!
Oh for the good old days of a "jail break" - cadets ending up in Hong Kong, F3822 + passport -> go!!