There are many other examples of this, but the one that occurred to me was that of Marie Krogh.
Marie Krogh (1874-1943) was a scientist and physiologist living in Europe. Around the turn of the century the theory of how oxygen got to the cellular level to be used in metabolic process was active secretion of oxygen by the lungs, it's adherents were the chief scientists of the day: Bohr and Haldane. To disagree with them about their theory was tantamount to professional suicide, similar to a first year undergraduate telling his Nobel Laureate department chair he was wrong in his work.
Marie Krogh, working with her husband August, published a paper in 1909 in the scientific journal Skand Arch Phiol refuting Bohr's active secretion theory, claiming oxygen actually passed across the alveolar-capillary membrane by passive diffusion; that the partial pressure of oxygen, higher in the alveolus, passed to the lower partial pressure present in the capillary.
Then she did something that to me was remarkable: she described a test that could test the theory by delivering a small concentration of carbon monoxide to the lung, measuring the percentage inhaled and exhaled, and calculating the amount passed into the blood stream. She also calculated a 'constant', a mathematical factor that would be needed for the calculation of the transfer factor of oxygen.
The rub was that there was no way at the time to determine if she was correct. There were no mechanical devices or sensors that could perform the test.
In 1957, a noted pulmonologist, C.M. Ogilvie, read her paper published nearly 50 years earlier, and decided it could be done. Her theory and even the mathematical calculation of the constant turned out to be correct.
She didn't live long enough to see her theory proven, but I'm sure she had no doubts.