Recently, for the first time, I had the occassion to edit a tiff file (scan from a slide) using ACR. I was very pleased with the outcome. When I finished editing the image, I simply clicked "Done". When the tiff was reviewed in Bridge, and when subsequently opened in PSCS3, the edits were intact. I began to wonder where the editing "instructions" were stored. I know the edits were "parametric" or nondestructive, because I can open the image again in Bridge and revert to the original image using "Develop Settings" I assumed they would be somewhere in a sidecar (xmp) file, but I can find no such file in the folder or elsewhere on the drive. In Camera Raw Preferences I had selected "Save image settings in sidecar ".xmp" files.
Any clues?