Erlo Stegen's sermon 'A Lot Was Lost' emphasizes the consequences of Lot's carnal choices compared to Abraham's spiritual walk. Lot, who sought worldly gain and comfort, ultimately lost everything, including his wife, due to his failure to follow God's path and seek wise counsel. The sermon challenges listeners to examine their own lives and decisions, warning against the dangers of living in the flesh and the leanness of soul that can result from pursuing personal desires over God's will. Stegen highlights that while Lot is referred to as 'righteous,' his decisions led to significant loss and suffering, urging believers to prioritize spiritual over worldly pursuits.