I went through the 4 day ALPA accident investigation course in Herndon right after this happened.
The instructor was a TWA guy who had been on one year leave (paid by the insurance company) to work on the wreckage.
He said that a missile, even a kinetic or dummy warhead missile, would leave a series of aligned holes in whatever structure it hit. Think of a .22 bullet hitting a line of mailboxes. There would be damage that could be lined up like a laser. This evidence was not found.
Remember that TWA lost close to 50 employees on 800, working and non-rev. NOBODY was more motivated to find the cause than the TWA investigators.
The explosives residue was leftover from a dog training event, as I recall.
If you guys are trolling for conspiracies, I'd look at the Egyptair crash. On the previous leg, the pitch trim caused the autopilot to click off TWICE. Then it gets out over the ocean and crashes. Obviously a suicidal pilot. Remember, he said, "Allah Ahkbar!" as the plane nosed over. What would YOU say if presented with an uncommanded pitchover over the ocean?