Help--strange noise like dragging something coming from rear driver's side...

Mazda3 s
About a week ago, I heard this scraping noise and thought I was dragging a branch or something. It happened a few times, then stopped. I checked and saw no branch or anything hanging under the car, so I took it to my mechanic. He put it on the lift and couldn't find anything obviously wrong. He wanted to replace the bushings (?) on the rear wheels for around $300 but I said to hold off as the noise had stopped. I haven't heard the noise since. Any ideas? Has this happened to anyone else? I have a 2006 Mazda3s sedan. Thanks!


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'18 CX-9 Signature
Maybe it was a rock that got caught between the brake rotor and pad? That's happened to me a couple of times on previous cars. Could have also been a branch or some other road debris that eventually came loose.