They cannot recover in restitution unless the court holds that there was a material breach. If the court holds that there was a material breach, Osteen and Brianna would have to seek a remedy for breach of contract--expectation, reliance, liquidated damages, cost of completion, specific performance.
Seeking expectation damages is typical. Reliance typically provides a smaller recovery than expectation; there is often no liquidated damage clause; cost of completion is only appropriate for uncompleted or defectively completed projects; and, specific performance is typically not available.