Ah yes, like the one time I got to fly on Concorde (a single sector) and my 'reserved window seat' did not exist at check in ...
This thread has caused me to go back online for my next long haul booking and print off the seat reservations. Then it's more than just my word!
Incidentally, whilst on the VS website, I noticed this statement, pertinent to the observation by tdracer above:
Information for passengers who are booked to travel on a Delta Air Lines flight
Please check your ticket to see which airline your flight is operated by.
For Virgin Atlantic flights, please proceed to My Booking to retrieve your flight. For Delta Air Lines, please proceed to My trips on Delta.com, to manage your flight.
They also hot linked the pages.