Well...it just happened to me. And no, my pattern wasn't "borrowed".
I just finished off a new clutch this weekend. 100% me. Most of it was even freehand. I drafted out the basics: handle & body. I pleated the body & curved the sides after I sewed in the pleats to give it shape.
And this evening I took some pics and then checked my email while they downloaded. I had lots more to pic than just the clutch.
Lo & behold...my newsletter from The Fabric Shopper had advertised a pattern for a clutch that is nearly identical to the one I just made. And I know I have never seen it before. I guess there are just only so many ways to make a basic pleated curved clutch with a flat attached grip handle.
So if you see something out there that looks a lot like yours...it doesn't necessarily mean that someone "borrowed" the pattern. It's all in the individual touch you give it that makes it yours.
So...here's my Bizarro clutch:
And the pattern I saw tonight...after the fact...