[Aram]

Did this happen in a lang hive or in a TB with frames. If in a Lang, just remove the whole deep box, place on its side there will be much less bees in the air, they'll be a bit confused but much happier to be still together than if you take it apart and expose each frame. The broken comb will be at your finger tips. Just use smoke or a brush to chase the bees off of it and collect. Depending on the quantity and state of the broken comb it might not be worth retying to top bars, I'd just remove it altogether. If you have a swarmframe it's not too difficult. You can also lean the comb with brood upright against one of the hive walls with no frames or bars above it. REmove it after the current brood hatches, the queen will not use those cell if she has any other comb availabile. I've done that but never found out if the brood hatched or died and the bees just cleaned out the dead larvae ???
It's tough for the bees to do a proper attachment to the bottom bar of a frame (I've done that too for various reasons and often it end up in a lot of work later.)

 

[kenny61]

I would wire some Girls hair clips to the underneath side of the top of the bar and clip the comb to it..the bees will reattach it..ive done this with cross comb in a top bar hive and it works great

 

[honeybeekeeper]

If it happened in your TBH your gonna have to make room to reach in with both hands to bring it up out of the TBH. I would use a cheap cookie sheet to work on so you can reattach it to the top bar and then lower it back in. Yes the ladies will not appreciate you reaching for the brood comb but it has to be done. The faster the better!