Artists can (and often do) come up with similar ideas, independently of one another. Just this weekend, I was looking at Pinterest and happened to see this lovely print by Jaime Derringer of Design Milk. I've been making a similar pattern without ever having seen Jaime's print...a genuine mistake on my part to not research the pattern better. I didn't intend to copy Jaime and was genuinely mortified when I realized that I had been drawing the same pattern. With regard to the current U.O. situation, it's very clear that several artists have been making very similar work (see this post on Regretsy). Who came up with the necklace design first? I'll admit that those waters are pretty murky.
Here's the thing though: this isn't the first time an independent artist has cried foul. Urban Outfitters and Cody Foster & Co have repeatedly been accused of stealing ideas from independent artists (people like you and me!) and are making a profit from these stolen ideas. Do I really need to say this out loud?! Making a profit from stolen work is not OK.
Abby from abby try again wrote a really interesting post about this topic and Renee wrote a post about this specific case