Income tax Acknowledgement No.

Dear Friend

I had filed incometax return online of my various client, i got efilling acknow. no., sent physical copy of acknow. at bangalore,  after a few day i got reply from bangalore through Email that for so and so acknowledgement number physical copy of Acknow. yet to be received.

My problem is how  should i figure out acknow no. relate to which client. ( because reply has contained only acknow. no. )