If you have just made a successful landing in the A320, and you don't set proper TOGA power, what mode does the automation revert to? What will the FD show? Will it be approach mode and basically only show a localizer perhaps? I'd doubt anyone will try to fly a FD with the vertical guidance showing level or just completely missing for a takeoff roll...
The scenario just sounds like a bit of a reach honestly. But who knows. I'd still put my money on some sort of technical issue or perhaps the dual input issue.