Legal Issues

My friend purchased a lorry in 2012 but the registration of the vehicle is in his close friend's name who helped him in getting the vehicle but unfortunately, my friend died in 2017. Now the loan of the lorry is clear but the person says he has given 3 lakh to my friend but he has no written proof of this and the person is also no more. Now, what legal action can my friend's family members do in this case? Can they demand compensation if the person says the lorry belongs to him as my friend died in another state when he went with the lorry to unload goods due to a heart attack? If he is the owner then his driver who died of heart attack his family members, can demand compensation from the owner or not are they legally liable for compensation.