The initial lām of lajaffa belongs to the answer, not to the particle. It commonly appears with affirmative past counterfactual answers, but is not universal.
Opening interactive controls...
The Answer’s Lām
Exhortative Particles: Urging, Reproach and Two Uses of Lawlā
The initial lām of lajaffa belongs to the answer, not to the particle. It commonly appears with affirmative past counterfactual answers, but is not universal.