Are we all jumping the gun a bit?
It may just be missing from that PDF timetable.
The PDF timetable for
Monday 26 August is showing several trains with codes for
Fridays Only and Fridays Excepted at the top of the column, so I think we can safely assume there are a few mistakes in it.
The 1429 starts from Manchester Piccadilly at 1355, and Virgin's "spanner" page mentioned upthread says:
Services between London and Manchester
From Saturday 24 – midday 26 August a reduced service (two services per hour) will operate between London and Manchester.
Your train is after midday on 26 August, so a normal timetable
should be in operation by then.
Just looked and your train is still showing up with Advance tickets available. It might be worth printing off an itinerary showing that train (if you don't have one with your booking confirmation), so you have proof just in case that train does get deleted in the next few days.