Where is my Moral compass pointing?

A year ago I swiped my credit card at a small store for 3500/- purchase. Unfortunately the cashier forgot to add 2 zeros for paise hence billing me for only 1% of the purchase value. Even though this was not due to any fault or malicious action on my part, I felt guilty and sorry for the shop owner. I imagined myself as one of the shoplifters or swindlers and saw to it that the error was rectified.
However 2 months ago a friend of mine used my credit card to purchase a digital camera from an online corporate store for 28000/- and due to some billing problem my credit card was not charged for the shipment. Unlike the previous case, correcting this glitch won’t involve any financial cost for me. On the contrary, it would have helped me retain my moral high ground. Yet through my inaction I defrauded my online store, but what is worse is that I had no qualms about it.
There could be several plausible explanations for it:
1. 28000/- might be too tempting an amount for me. However I personally did not benefit from this transaction.
2. Paying back in own coin. However I never felt that this particular store or bank had cheated me in the past and have no grudge against them.
3. I remembered what my mentor had once said… During the 18th century the pious, just and gentlemen could commit genocide and atrocities against the black slaves and yet never regret it. This was because of the simple fact that these whites did not empathize with the blacks. To them they were no more than some exotic creatures that bore close resemblance to humans. (In no way I am endorsing this thought) There is a possibility that I sympathized with the small store owner but not with the corporate.
I am having this strange feeling because I am worried not because I did wrong but because why I did what I did.