The 5 billion was only the unions share of the stimulus money that was given to GM so that it could pay us back for some of the money that they owed us. That does not include the "investment" we have in GM. That will probably be another 10 or 20 billion loser, depending on how the stock deals work out.
Just for kicks...FedGov owned 60.8% of GM before today. After today, if I understand correctly, they will only have a 37% equity stake in the company. The problem is they only raised $11.8B (ish). Just doing the math in my head, they are going to fall woefully short of recouping their original "investment" of $42B, unless the GM stock price rises, exponentially. I'm not holding my breath.