使用过去分词Undeterred作状语，简洁地表达了“未被吓退”的状态，同时once引导时间状语从句，逻辑清晰。
A merchant operated a stationery store on a street, primarily selling notebooks and paper products. With several schools and government offices nearby, his business was consistently thriving.
However, the onset of the rainy season disrupted this stability. Floodwater rushed into the store, soaking most of the inventory and nearly wiping out his entire capital. Undeterred, he borrowed money to restock once the rain stopped. But just a few days later, heavy downpours returned, submerging his new stock once again.
While his employees frantically tried to save the paper, he silently pushed open the door and disappeared into the rain. A few days later, he sold the storefront. Many assumed he had failed completely. Yet, shortly after, he reopened elsewhere on the same street, still selling paper products. People mocked him for stumbling at the same hurdle. When the rainy season arrived again the following year, people were astonished to find that while other stationery stores on the street suffered severe flood damage, his store remained safe and sound. Moreover, his sales surged several times during that period, quickly recovering his previous losses and turning a profit.
In reality, during that heavy rain, he had walked the entire street, identified the highest ground, and leased a shopfront there at a premium price. It was this flood-proof elevated location that enabled his remarkable comeback.
一位商人在街边经营一家办公用品店，主营各类笔记本和纸张。得益于附近有多所学校和机关单位，生意一直颇为兴隆。
然而，雨季的突然降临打破了这份平静。洪水涌入店内，浸泡了大批货物，使他几乎倾尽所有积蓄。但他并未气馁，雨停后立即借钱补货。不料几天后暴雨再次来袭，新进的货物再度被水浸泡。
当店内员工手忙脚乱地抢救纸张时，他一言不发，推门消失在雨幕之中。几日后，他转让了店铺。旁人皆以为他彻底失败。然而不久后，他在同一条街道的另一处重新开张，依然经营纸品。众人嘲笑他愚笨，总在同一处跌倒。直到第二年雨季再次到来，人们惊讶地发现，街上其他文具店都遭受了严重水患，唯独他的店铺安然无恙。更令人瞩目的是，那段时间他的销售额翻了几倍，迅速弥补了此前的损失并盈利。
原来，在那场大雨中，他遍历了整条街道，精准地找到了地势最高的位置，并以高价租下了那处铺面。正是这块雨水无法浸及的高地，成就了他的东山再起。