I think that you acted correctly, without any secondary indication of anything wrong, I would have been inclined to finish my meal.

Here in London I have heard at least three terrorist bombs explode, in each case nothing would been gained by panic or running around.
I was not close enough to be injured, running around would be as likely to lead into danger as away from it.

The first bomb I heard was about 20 years ago it was 50 yards away, but was only a small one.
The next was a large vehicle bomb, I was a mile away, and saw no need for any special action.
The most recent was the one on the London undeground, near Aldgate station. I was employed in the basement of a large office building relatively near the explosion.
I was uncertain if the noise was a bomb, or a railway accident, but a deep concrete basement seemed a good place to remain.