If a hidden Hidden Blade targets a unit at one battlefield, but the unit moves to a different battlefield before Hidden Blade resolves, what happens?

Ruling: Hidden Blade will mistarget and have no effect. The unit will not be killed and no cards will be drawn.

Sequence:

• Hidden Blade is played hidden, targeting a unit at a specific battlefield
• Before Hidden Blade resolves, the targeted unit moves to a different battlefield
• When Hidden Blade resolves, it mistargets because the unit is no longer at the original battlefield
• No unit is killed and no cards are drawn

Nuances:

• Hidden cards that target have the implicit text "here" added to their targeting requirements
• The target must remain at the same battlefield (the "here" requirement), even though it hasn't changed zones
• Moving to a different battlefield makes the target no longer legal, even if it's still on the battlefield