Easily. There were lots of unaccounted for stingers in...drum roll please...Afghanastan at the time. The plane, according to a FR thread, exploded at around 5,500 feet.
There were lots of reasons, including the Atlanta Olympics, why the WH wouldn't want to deal with a major terrorist incident at that time.
Wrong, the initial explosion occurred at over 15,000 feet. The detonation of the wing fuel tanks occurred around 5,500 feet.
Secondly, IR missiles would not have caused the center fuel tank to explode. An IR missile would have taken off an engine at most.
The initiating event occured as TWA-800 was climbing through 13,800 feet... the massive fireball at 5,500ft. was a fuel explosion that did occur when the truncated plane had lost one of its wings and had spilled all of that fuel into the atmosphere which then ignited. That was not the missile.