In Grid as Subgrid, select a sub row then you will find a father row which with same row id is selected.

This bug can be find in "http://www.trirand.com/blog/jqgrid/jqgrid.html"

Advanced => Grid as Subgrid => page 8 to 30 => "plus" left in row 13 => select sub item row 13 => dropdown father gird => father grid row 1 at bottom is selected.

Thank you.