There are two men that received visions during the Millerite movement that Ellen White mentioned in various places--Hazen Foss and William E. Foy.
Hazen Foss was not a Seventh-day Adventist. Prior to the Great Disappointment, Hazen Foss received a vision yet refused to share it (particularly due to his disappointment on Oct. 22, 1844--he said "he had been deceived" by the Millerite teaching). A short time later, he heard Ellen White relate her first vision. After hearing her describe what she saw, Foss believed that God had taken the visions from him and given them to Ellen White. Ellen White mentions these details in a private letter, but neither affirms or denies Foss' claim. It would seem that the remainder of Foss' life was rather miserable. He apparently believed that the Spirit of God had departed from his life because he refused to share his vision and became greatly depressed.
The story of William E. Foy is quite different. Foy was a Freewill Baptist and received at least four visions during the Millerite movement. Unlike Foss, Foy continued to share his visions and preached on the second coming until his death in 1893. The idea has circulated that Foy also rejected God's commission to share the visions, but this is not true--he preached for some 50 years.
While one man refused to share his vision, the other did do so repeatedly. That three people (Foss, Foy, and Ellen White) had similar visions around the same time suggests that God wished several people to spread the message of His soon return, rather than limit the gift of prophecy to a single person or a single gender. In regard to Foy and White, it is evident that they had different callings and that God used them both in different, yet harmonious, ways.
For more information on Hazen Foss, see Ellen G. White to Mary Foss, December 22, 1890, LT 037, 1890; Michael W. Campbell, "Foss, Hazen Little," in The Ellen G. White Encyclopedia, Denis Fortin and Jerry Moon, eds. (Hagerstown, MD: Review and Herald, 2013), 378-379.
For more information on William E. Foy, see Delbert W. Baker, The Unknown Prophet (Hagerstown, MD: Review and Herald, 2013).