Can I play a unit to a battlefield from the trigger of Baited Hook if I sacrificed the only unit at that battlefield?

Ruling: Yes, you can play a unit to that battlefield using Baited Hook even if you sacrificed the only unit there. Because the game is in a Closed State while the ability resolves on the chain, you do not lose control of the battlefield when it becomes temporarily unoccupied.

Sequence:

• You activate Baited Hook by paying its costs and declaring a target friendly unit to kill
• The ability begins to resolve (game enters Closed State with active chain)
• The targeted friendly unit is killed and sent to the trash
• You look at the top 5 cards of your Main Deck
• You choose a unit with appropriate Might (up to 1 more than the killed unit's Might) and play it
• You may place that unit at the now-vacant battlefield or any other battlefield you control
• The chain resolves and the game returns to Open State

Nuances:

• The killing of the unit is not a cost but occurs during resolution of the ability
• Battlefields only become uncontrolled when empty during an Open State, not during a Closed State
• As long as a chain exists (ability or spell resolving), control of battlefields is locked
• This same principle applies to other effects like Arcane Shift that temporarily vacate battlefields during resolution