There is hepatitis A, B, C, D, E, and G. Why did they decide to skip F? All I can find online is that there is no hepatitis F virus, but that doesn't explain why there is hepatitis G and not hepatitis F.
A virus isolated from rare blood samples was believed to be able to cause hepatitis, and this virus was designated as the hepatitis F virus. (Source: MedicineNet)
Further investigation has failed to confirm the existence of this virus. There is no known hepatitis F virus.
For more information on the candidate Hepatitis F virus, see Fagan & Harrison (1994).
Fagan, E. A., & Harrison, T. J. (1994). Candidate hepatitis F virus in sporadic non-A, non-B acute liver failure: exclusion in liver of hepatitis viruses A, E, C and B by polymerase chain reaction. In Viral Hepatitis and Liver Disease (pp. 73-76). Springer, Tokyo. https://doi.org/10.1007/978-4-431-68255-4_19