While replacing an outlet, a hot [black wire] accidentally touched the ground wire. There was a shower of sparks for just a second. Now there is no power to the hot wire. I checked the breakers, and none were tripped. It is possible that this circuit is wired into a GFI breaker, but the GFI breaker still said "ON" and was not apparently tripped.

Well, first off, by default I have to lambaste you for working on it hot. WHAT WERE YOU THINKING??


Do you know which breaker it is? Is it a GFI breaker or not?
It may have tripped but not moved. Did you try to turn the breaker off then back on?

Do you have a tester?

It could also be protected by a GFCI receptacle somewhere. Check for any that are tripped. And stop working on hot circuits, we'd prefer you continue to live.