So, what you mean is you want to scroll the DataGridView to the top, correct? Scroll bars scroll, so using the word "scroll" would have been the best way to describe your issue.
You probably can't find it because you were making assumptions about what it would be called. In cases where you can't immediately see what you want you've just got to open the member listing in the documentation and start reading down the list. Doing that, I'm sure you'd have known that you'd found what you were looking for when you saw the FirstDisplayedScrollingRowIndex describe as:
Gets or sets the index of the row that is the first row displayed on the DataGridView.
Set that property to the index of the first row, i.e. zero, and you are good to go.