When disconecting battery I saw a spark

Hi all,

I was going to change another lcd as always, but today i forget to shutdown the iphone and also i forget to unplug the battery with a plastic item.

When I was unpluging the battery connector I touched somewhere and I saw a spark, after this I tried to connect again the iphone and it just dead.

Do you know what I possible need to change for solving this short circuit?

Or how can I debug or troubleshoot what is wrong now and need to be changed.

Thanks