I just went out to dinner, when it came time for the check, it was just one big one and I didn't have small enough bills to cover my meal exactly, so I just waited as the rest of them were talking about how they were going to divide it up and I figured I would just ask one of them for change after they were done talking. But after they finished, they didn't even notice that I hadn't put in any money so I didn't say anything and just put the money I had out back in my wallet. Apparently they put all the money there and didn't even notice I hadn't put anything and nobody asked me or anything. I didn't even bring it up afterward because I thought they would get mad or something. Did I do a bad thing? Or was it just an unfortunate circumstance where it just happened to end up that way and I got a free meal? Please tell me what you guys think I'm very conflicted about this.

Some more details if this matters, we all ordered approximately the same amount of moneys worth of food, and I guess someone else didn't do the math correctly and put extra. They were also largely ignoring me at that point.