The names of the internal layout objects from ggplot_build changed slightly.
ggplot_build
get_panel_y_range(layout, index = 1)get_panel_x_range(layout, index = 1)get_panel_params(layout, index = 1)
get_panel_x_range(layout, index = 1)
get_panel_params(layout, index = 1)
layout part from ggplot_build
layout
Could be panel number?