What Happened to the Engineers? [Minor Spoilers]

At the end of Halo First Strike, It is said all the Engineers on board the Ascendant Justice were transferred on board the Gettysburg, prior to the Admiral making his last stand. But in Thursday war Parangosky (I think) said the Onyx engineers were the first they had besides Virgil. So My question is what happened to the 100 + engineers on the Gettysburg?