I'm pretty sure this is just a preview issue. Try saving a PDF of your InDesign layout, and then check the PDF. I bet it will look okay. If you have Adobe Illustrator, you can open the stock vector and re save it. That might fix the preview.
I created a work-around for this issue. I opened the original downloaded AI file in Illustrator, selected the vector artwork and pasted it into a new file. I saved that file as an EPS and it placed correctly in hi res into InDesign.
I tried your fix before I posted my message and that did not work. I created a PDF and the image was still pixelated as it appeared in InDesign. Your response is not a "Correct Answer."
It sounds like the stock vector file had a corrupt preview. I would have done the same thing as you to check it and fix it.
I haven't yet run across this issue with any licensed vector files myself though. Have you seen this happen before?
I'm sorry to here there was an issue with the file, but glad you found a workaround. If you can provide me with the image ID we can let our content manager know.
No, Adobe Stock images and vectors have been working out great for me, all except for this one.
The image file I was working with is located here: Vector Meadow mood Engraved fractal outlet composition - image | Adobe Stock