/johnny
There really is no swap. The payroll taxes collected go immediately into non-market, interest bearing T-bills that are backed by the full faith and credit of the USG. They are IOUs just as much as any T-bill is.
Where would you want the SS "surplus" to go? It was/is a massive amount of money. We are no longer running a surplus and won't unless the program is reformed. The main problem with SS is not that the USG "stole" the money, but rather, the program is flawed actuarily (as is Medicare which has been running in the red since 2008). With 10,000 baby boomers retiring a day for the next 22 years, there is not enough money to pay the benefits promised. The entire SSTF will be gone by around 2035 and then reduced benefits will be required.
The real problem that is being caused now by SS is that it is running in the red and therefore, some of the T-bills in the SSTF must be cashed in to make up the shortfall. The General Fund has been running in the red for more than 60 years. Hence, we must borrow money to redeem the SS T-bills. During the period 1983-2009 SS was a cash cow. Now it is becoming a black hole. In 1983 when SS was running in the red, Reagan struck a deal with Tip O'Neill that increased SS taxes and decreased benefits. Something similar must be done now to save SS. Personally, I would prefer privatization, but there is not the political will to do so.