If you cannot find the will after a diligent search you, or the parties authorized by statute, will have to file for intestate probate (probate without a will).
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If no will can be found and no one can testify as to its contents based on personal knowledge, the estate will be distributed by the probate court under the laws of intestacy. Your father and his siblings will share the estate.
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First look in the safe deposit box of the deceased if possible. Then look where the deceased kept their important papers (i.e. insurance policies, deeds to real estate, passport, marriage certificates etc.). If that still doesn't yield the document, then you'll have to open a Probate in Clark County on an Intestate basis and law of Nevada regarding Intestate Succession will apply.
If a will is not found, property passes intestate. Nevada has a statute that sets forth the succession without a will. Someone does have to file a petition with the court to appoint an administrator if there is no will. Titled property cannot pass without a court order.
Your question points up a potential problem with wills. Wills don't automatically get filed. Some people give a copy of their will to one or more relatives to increase the chance that the will will be filed. However, in other cases, the person who writes the will does not want the relatives and friends to see a copy of the will before death because the will writer doesn't want to offend people or get lobbied.