Gst sale bill missing during march 2018, but itc claimed by purchaser , now what should i do ?

During Annual return of GST it has been found that , One of my clients have 3 gst sale bills completely missing ( both GSTR 3B AND GST 1 ) for the month of March 2018  and purchaser have already claimed input tax credit of that 3 bills .

Now from seller point of view , Now at present  Is it possible to show  3 missing sale bills for the month of March 2018 into GST 1 ?

If No , then how could i rectify the above problem ?

Thanks