no will

I posted yesterday a question regarding quick claim deed and no will. In short my dad died leaving no will. His wife has quck claim his property for the sum of one dollar no warranty deed, she did not file a probate or estate. her name was on a quick claim deed my dad did in 1991. However in Il if you die without a will half of the estate goes to his surviveing children. she cleaned out his personal property and CD's. Aution everything and did not contact his serviving children. We think there was a will. She say's no. How can we find out if one exsisted and what should I do. Can we hold her resposible for half of the assesd value. She quick claimed it for one dollar. Do I need a death certificate on my dad. Thank you for helping