I received a check for unclaimed property from the state of Nebraska. there wasn't any forms like the 1099 with it , so is it considered taxable income?

No, unclaimed property is not taxable.  However, any interest that had accrued would be taxable and the state issuing the unclaimed property.  For example, if you had a 500.00 life insurance policy that was unclaimed and interest had accrued on the policy of $23, you would owe taxes on the $23 in interest.