Estate Law Questions? Ask an Estate Lawyer.
If there was never a probate case opened to settle his estate, then you would have to do so and then be appointed Administrator of his estate. You would then have the power to contact any financial institutions that he had accounts with and request information about whether he had assets solely in his name or whether everything was jointly owned.
But if everything was in both their names, then the wife would have automatically become the sole owner upon his death. She wouldn't be able to access any accounts that were solely in his name, so it would have been in her best interests to file a probate case to settle the estate if there were other assets because she would be entitled to the first $50K and half of anything over that.
So it stands to reason that if there were assets solely in her name, she would have filed a probate case so she could get that money.