Hi,
I am in the boat as you. I submitted my paystubs (clearly mentioning that I received cash, stamped & signed) along with a 'Letter of Explanation' describing everything like I was getting paid in cash and I used it against my personal/ household expenses which is why it didn't end up in the bank.
He might call you back again after you submit the documents, so don't be nervous & try to be as clear as possible to make your point, as you would need to clear his doubts.
Good Luck!