Let’s say the following events occur. (I have a friend who is wondering…)

1] You purchase tickets online to an event
2] You arrive at the event, and the box office agent has you recorded as having purchased twice as many tickets as you are aware of purchasing
3] You protest, “I only purchased X tickets, and only received an online email receipt for X tickets”
4] Box office agent queries boss, and receives permission to resell your extra tickets and hand you the cash.
5] It is emphasized this isn’t normally done, but the boss OKd it, and you express your gratitude.
6] You return home, check your online bank account, and confirm – only one set of tickets was purchased
7] You realize you basically attended a free event, but the venue is out $X. (You did purchase drinks while there, so they did make some money off you.)
8] But you also realize the boss gave the OK, so the box office peon isn’t going to get in trouble for it if the likely electronic blip is discovered.
9] The facts don’t change in your bank account – let’s hypothetically give it a week.

Do you feel morally obligated to return the extra cash to the venue?
Or is this the Monopoly-equivalent “Bank error in your favor, collect $X”