This is no help at all, but I'd take a guess that this information did at least exist in 1912.
When Olympic reached New York, and this was a week before it's nex departure, the White Star issued a statement that a large number (they actually gave the number but I can't remember it) of passengers were already booked to sail the return maiden voyage back on Olympic.
Certainly those booked into Titanic received refunds or a transferal to another WS ship. Some names of these people do exist in books somewhere. I believe Steven Biel mentioned one in his "Canoe" book.
I remember reading at that Henry Adams, the author/historian, was to be on board the inaugural run out of New York.
At least with the upper classes, wasn't Spring the time when one went to Europe rather than return from it? If so, I'd think the trip out of New York would have had a passenger list that was comparable with that from the maiden voyage.
Darren, I think you picked an interesting topic to start a discussion thread with.
One of Titanic's stewards wrote a postcard home to say that it was an easy trip out as the ship was only partly full but he understood that the return trip would be booked solid. Nice to get hold of one of those return tickets eh!
According to a great new book called "Ladies and Not-So-Gentle Women" by Alfred Allan Lewis which is a joint biography of Anne Vanderbilt, Elisabeth Marbury, Elsie de Wolfe, and Anne Morgan (JP's daughter), not only was Henry Adams planning to make Titanic's return voyage but Anne Morgan was as well. The author claims that she, along with an entourage of family and friends,had been booked on Titanic's April 20 voyage but postponed their travelling plans after the disaster. They all finally did set out aboard the France on May 2, 1912, which was the return voyage of its maiden trip.
Those in the Morgan coterie who were to have sailed on Titanic April 20 were (besides Anne Tracy Morgan):
Elsie de Wolfe
Mrs. J.P. Morgan (Anne's mother)
Mr. and Mrs. Herbert L. Satterlee (sister/brother-in-law)
Alfred Allan Lewis points out that it was strange indeed that Morgan and Company chose to take a rival ship when Dear Old Daddy's Olympic was leaving NY only 2 days later. (Perhaps knowing it had not yet been fitted with sufficient lifeboats had a hand in that decision!)
The author does make a curious reference to Henry Adams in connection to Titanic. He says that Adams had suffered a stroke that spring at his home in Washington. How he would then have been in good enough health to sail on Titanic is not addressed.
Lewis writes that Adams was
"...deeply saddened to find two friends among the passengers who had not survived: the painter Francis Millet and Archie Butt, Roosevelt's aide who had been so impressed by Anne Morgan when Bessy (Marbury) and she had lunched at the White House..."
Lewis quotes a letter of Adams's to a friend which shows the strain on him of the news of the Titanic:
"...The foundering of the Titanic...strikes at confidence in our mechanical success. By my blessed Virgin, it is awful! This Titanic blow shatters one's nerves. We can't grapple it..."
Sounds eerily similar to our own reaction to recent catastrophic events.
PS) Anne Morgan was one of the organizers of the Titanic Relief Committee. She was on the pier herself the night Carpathia arrived to help survivors who needed immediate assistance.