IF Swift disappeared from Booking Platform

[Steven]

They send you a text message if your sailing is in doubt or cancelled,

Perhaps the people concerned dont have a mobile phone.

I'd say its more likely given these people were posting to Facebook and Twitter that there has been some sort of issue with the automated messaging system!  A single text message when the company know that far out would seem a bit odd given we know Irish Ferries can send an email to everyone booked on a certain vessel for example.  They proved that with the W.B. YEATS cancellations!  Good customer service would be to even telephone the people concerned rather than relying on them to read a text message (my mum wouldn't have a clue despite having a mobile phone) from an unknown number!  (A pet hate of mine that most if not all companies in the travel sector are guilty of).