What are you trying to do? Do you mean the actual screen tap coordinates or the grid coordinates?
There are no coordinates for section headers; the SDataGridCoord class is for the cell object.
The closest thing would probably be the coordinates for the first cell in the section:
- (BOOL)shinobiDataGrid:(ShinobiDataGrid *)grid shouldCollapseSectionAtIndex:(NSUInteger)sectionIndex
SDataGridCoord *coord = [[SDataGridCoord alloc] initWithCol:[SDataGridColumn columnWithTitle:@"forename"] row:[SDataGridRow rowWithRowIndex:0 sectionIndex:sectionIndex]];
NSLog(@"Coordinates of first cell at section: %@", coord);
// I don't know why cell is null; maybe ShinobiSquad has an idea.
SDataGridCell *cell = [grid visibleCellAtCoordinate:coord];
NSLog(@"Cell at coordinates: %@", cell);