At my first job, we had paper time sheets. At the end of the work week we'd have to fill out the days and hours we worked so we could get paid the right amount. Sometimes I'd forget, so when the accountant wanted to do pays she'd have to come find me to get me to fill it out, much to her annoyance.
One week I didn't work at all because we got rained out, and yet I still got paid for the whole week. I can only assume that the accountant thought I didn't fill it out again but was too annoyed to get me to fill it out, so she just paid me thinking I did a full week.
At the time I felt a little guilt over not telling anyone, but it turned out everyone in the main office were absolute monsters.
They had this inner circle thing going on, except the inner circle was literally everybody except for me.
I was there for years and never got invited to a Christmas party. I figured it was because they didn't have Christmas parties, but it turned out they had secret parties every year and everyone was told to keep it a secret from me. Just me, no one else. Apparently they thought I was an “autistic robot”.
After all of that, I had absolutely no guilt over keeping that money. I felt absolutely horrible when I found out they had purposely excluded me from work events because they didn't like my personality. All I did was keep my head down, work hard and not really talk to anyone. When I did talk I sounded like a “monotone robot”, which means I'm autistic according to them. Apparently that means it's okay to exclude me from work events.
Even with that extra money, I still feel like they owe me more.