I don't know if ayone has any exact numbers on this one. There was quite a bit of confusion at the time even trying to find out for sure who was actually aboard. I don't know if this will be helpful or not, but if you get a copy of Debbie Beavis's "Who Sailed on Titanic", it'll give you some good insights into the problems.
Quite a few survivors were listed as dead in the time soon after the wreck. Off hand, I recall the Stengels, Mrs Malvina Cornell, Leontine Aubart and Mauritz Björnström-Steffansson.
An example of the reverse was Alfred Cunningham, one of the H & W workers, who was incorrectly listed as a survivor. He was probably confused with Andrew Cunningham, a steward, who survived. He is still named as a survivor in Shipbuilders to the World, a semi-official history of H & W.
Even people who were not on board were listed as dead, notably George Eastman, the Kodak man. Conversely, I've seen Lady Cynthia Asquith listed as a survivor, but she was not on board either.
Marshall Drew was listed as missing (Master Marshall Drew) due to the fact that after being hauled up the side of Carpathia in a sack and dumped on deck, he heard a steward mention cocoa and doughnuts in the diningroom and scurried off to get some when the names were being taken on deck- he enjoyed showing the entry to people.
There were a number of people who originally booked to sail, but did not. The Cave List shows 7 such names. I once saw an April 15 newspaper article that gave a long list of 1st class passengers. Although I can't say the list was accurate in every respect (several passengers being listed 3 or 4 times under different spellings), it did list many of those known to have been on Titanic, those who are known to have booked but cancelled, and other names of people who presumably booked but cancelled.
Vanderbilt's name was among them, so he must have booked but cancelled just before Titanic sailed. Craig Stringer and I speculated he might have even booked the C62/65 suite.
PS. There were two sets of Vanderbilts who apparently booked to sail on Titanic. One of them sailed on the Olympic with his wife, a week before Titanic. I believe this has been covered several times on ET before.
The other story regarding the Vanderbilts is that one of the families, it is said, had planned to sail on the ship: it is believed to have been Alfred Vanderbilt.
However, he had to change his plans, but was not able to retrieve the family luggage. Therefore, he supposedly sent his valet, Frederick Wheeler (there is a Frederick Wheeler on the 2nd Class Passenger List) on to the ship, with instructions to take the luggage home.
James Moody was erroneously reported initially in more than one newspaper as having survived. This caused confusing agony for his family, as might be imagined. Confirmation finally arrived in the form of a WSL telegram to his family that his name did not appear in a list of survivors on the Carpathia.
Greg, that reminds me of one the more hilarious captions in Thresh's book - one for the photo of Mrs Ismay, and the solemn information that she survived the disaster. Oddly enough, so did Lloyd George...George Bernard Shaw...Winston Churchill...
In several published accounts after the sinking, the name of my grandmother, Marjorie (Newell) Robb, was erroneously omitted from passenger lists; her name was replaced by that of her sister, Alice Newell, who was not on board the ship, having remained at home in Lexington, Massachusetts with her mother. In fact, I recall that the original Walter Lord's "A Night to Remember" contained this same error.