The battery drain is most likely a result of knocking something loose on the board. Its not uncommon to knock a filter or connector loose.
I would take a good look at the battery connector, any filters near it (I don't remember any close on an ip6+ but don't trust my memory) and more importantly, around the digi and LCD connectors. I would bet money on a filter being knocked off. its much more likely than a screen draining power. If it were the screen, I would expect a hot phone as a result of a short.