whatif the executor does not tell me about the policy

First, proceeds from Insurance policies "pass outside the Will" meaning that if a PROPER beneficiary can be paid they are not part of the Estate proceeding in Court.   Insurance policies that do not have a beneficiary named have a provision that states how the policy is to be paid out (who the PROPER beneficiary is).   Sometimes the policy is paid to family members and it lists how (spouse, children, etc.) but sometimes it is paid out to "the estate."  You need to find out how your Father's policy is paid out when there is not a named beneficiary.  If you know the name of the Insurance Company and the Policy number (or sometimes your Dad's social security number can be enough) then you can try and contact them and see.  If the policy was to be paid out to people first and then the estate as I said before then you are correct: if you are the only child then with proper documentation the policy should have gone directly to you.  But these are a lot of "ifs" and you have to do some detective work here.

If there is an executor then your Father had a Will that has been filed in the Courts for probate.  Go down to the Probate Court in the county where your Father lived before he passed and take a look at his Probate file.  The proceeds from the policy should be in estate if they were paid out.  The executor has the obligation to account for all assets of the Estate.  If you suspect something is up find a lawyer to help you.