What level of seriousness is this, 0? Forgetting to ask for collateral or discussing it shows two people without any sense of what they are even talking about. A long-lived businessman like you (lol) and a serious lender like a bank will never make such a thing. Why? Because in 98% of the loan cases, collateral is the 1st and most critical issue that they discuss.
So now that he remembers that he didn't ask for collateral, you run here to ask for it. However, you forget (like him) that we also want collateral even for 1 satoshi. So, what will you do now? You will run to another forum and ask for 15BTC? This joke request becomes better and better every moment...