Man, that’s rough. Had a coworker pull this once, gave notice and just checked out mentally with days left. HR can’t force them to work, but they can dock pay for hours not worked or withhold final bonuses if that’s in the contract. A quick sit-down with a clear “finish this or it hits your paycheck” usually lights a fire. Worst case, document everything and shift tasks to someone else to keep things moving. Sucks, but it happens.