“Today, the federal government automatically puts all of the money that should be set aside for the Social Security Trust Fund into the General Fund. Raiding the Social Security Trust Fund was a precedent set in 1968 by another progressive president, Lyndon B. Johnson, to help pay for the Vietnam War.”
This is what I remembered. Once LBJ moved it from a trust fund to the general fund the government could raid it and replace the $$$ with T notes.
Never replaced with actual T Notes, they were "IOU's" or "promises".