[bsfgmzlj] Mistaking astronomical explosions for man-made

In 1967, a U.S. Vela satellite was orbiting the earth in an eccentric orbit.  The satellite was designed to detect nuclear-weapons tests, but it mistook a gamma ray burst for the explosion of a nuclear bomb.  (This detection was the first-ever observation of a gamma ray burst.)  How many orders of magnitude was this error, the mistaking of an explosion of one energy or power level for the explosion of another energy or power?

Is this the largest error science has ever made?  (Probably not: some early but serious predictions concerning the vacuum catastrophe were off by a factor of 10^120.  Modern predictions, while better, are still very far off from observations.)  Second largest?

The largest explosions produced by man coincidentally looked similar to, but in reality were comically smaller than, the largest explosions in the universe.