Can Stalking Wolf Ambush to the battlefield where you sacrificed your only unit?

Ambush at reaction speed fails if killing your only unit there leaves no units for the final legality check — the whole play is rewound. At normal speed while a chain is open, control has not changed yet so it can work. If you have a unit at both battlefields, Wolf can Ambush to the one that still has a unit; the emptied battlefield fails Ambush.