Second bonus in 'Navajo' chapter???

I collected almost every bonus but I am still missing the second bonus in the "Navajo" chapter. I looked everywhere but I couldn´t find it anywhere. Then I checked the web and it said that it is hidden near a grave and Jodie carries a blanket, which she places on the grave. That is weird. What should I do story-wise to get to that point? Can someone please fill me in? What must I do in order for this outcome to happen? I know that the grandmother dies during the ritual but after the ritual the "Navojo" chapter ends with Jodie saying good-bye to Jay, Cory and Paul and driving away on a motor-bike...

I would be very thankful for your help guys!