Should a lot or land owner suffer damage resulting from said drainage improvement and such party not have been notified thereof as provided for in section 31-909, such lot or land owner may, within thirty days from the date that said damage occurred, file a claim with the county board setting forth the nature of such damage and requesting a hearing thereon. A hearing shall then be had as provided for in section 31-910, with right of appeal as set out in section 31-911. Should assessment of benefits be made and a lot or land owner not have been notified as provided for in section 31-909, such lot or land owner shall have thirty days from the time of discovery of assessment or within one year from the date that said assessment is filed in the office of the county treasurer, whichever date occurs first, to request a hearing on the validity of his assessment and he shall have the right of appeal as set out in section 31-911 ; Provided, neither the failure to notify any lot or land owner nor the outcome of such appeal shall invalidate the proceedings as to other lot or land owners.