Your friend walks into a shop with a loaded gun and fails to rob it.
Turns out you owe this person money, now you feel that you no longer have an obligation to pay them?
That isn't an accurate scenario.
We are not talking about a friend in any way and it isn't independant from the tried theft.
Someone paid you to borrow your car for two days. The first day he tried to rob someone with your car, do you feel obligated to lend him the car for another day?
Of course not, I was never obligated to lend him the car at all. I'd have to refund him for the second day though otherwise he could sue me for the money.