The crash happened late last night in a creek between County Roads 3600 and 3900 near Independence, Kansas.
The Montgomery County Sheriff says emergency officials searched the area last night, but because of heavy rain and flooding, the victim was not located until early this morning.
Authorities say she was found a quarter of a mile from the truck.
They say she left a voicemail on a friend's phone saying she had hydroplaned and was in high water and needed help.
Deputies are not releasing the woman's name until family members are notified.