There is no definitive evidence or historical record indicating that Albert Einstein was sad or distressed during the last days of his life due to his inability to prove the non-existence of God or to establish that the universe was solely created by natural processes. It's important to note that Einstein's personal beliefs regarding religion and the nature of the universe were complex and evolved over time.
Einstein did express his views on religion and spirituality throughout his life, often emphasizing his reverence for the beauty and harmony of the natural world. While he did not subscribe to traditional religious beliefs, he did not identify as an atheist either. Instead, he described himself as an agnostic, stating that he did not believe in a personal God but was in awe of the mystery of the universe.
In Einstein's writings and interviews, he frequently referred to the concept of a "cosmic religion" or a deep sense of wonder and awe toward the workings of the universe. However, he also acknowledged that the existence or non-existence of God is a question that lies outside the realm of scientific inquiry and cannot be proven or disproven empirically.
Therefore, it would be speculative to suggest that Einstein experienced sadness or frustration specifically related to his inability to provide definitive scientific proof regarding the nature of God or the origin of the universe during his final days.