HCL Technologies — regarding copy of offer letter

Address: Elcot sez, shollinganallur, Chennai, Tamil Nadu

I have worked in hcl technologies, chennai from 30 april 2015 to 10 may 2016. I left hcl technologies to start my own business. But after 3.5 years i am again looking to pursue the job career. I got selected into one of the mnc in bangalore. They asked me to upload some documents, out of which hcl offer letter is also the one.

They needed offer letter to check my last salary structure. I somehow lost the copy of offer letter.

I requested for the copy of offer letter to one hr of hcl chennai. They responded by saying that they dont have access to that document now.
Kindly esclate the issue and help me get copy of offer letter.