While it happened on UA... This might be better suited to TS&S:
http://www.flyertalk.com/forum/trave...-security-222/
Now, to answer your question, seems they investigated, and were satisfied with the explination.
How much further would you suggest they take it? (and I am making a very broad jump here).... but an interrogation from a FAM? A strip search? Run them through the puffer?
FWIW,
little_1780 has a few "buzzing" toys. Hope no one would take him to the jetway for a "seconday search".