Took guy's ringmail from merchant but not sure if i payed..

So basically i took a ringmail from the merchant but it doesn't seem like i payed, when i tried to trade with the guy to give him the chaos orb he said it should already be deducted from trading with the djinn.. Should i be worried of being reported if im not sure i payed him? He seemed to not care either way..

If you're using the asynchronous trading system, payment is automatic.

They wouldn't allow people to just take the item and rely on the honour system; that would be rife with abuse.

Don't think you have done anything wrong. Technically, if you used the asynchronous trade, faustus is the NPC, not the Djinn, but it automatically does the payment if you have the currency, and you don't have to interact with the other player.