Reset metadata values :(

[OpticalMedia]

I worked on an image in camera raw for well of 24 hours tweaking and perfecting the image. I then decided to reset back to my default settings of 0 for everything to compare the images. When i opened the zeroed image in Photoshop bridge updated my metadata with that now i cant get my values back that i tweaked the image with. Is there anyway i can somehow get my metadata back or revert what  i did?

[Schewe]

For as long as an image is open in Camera Raw, you have unlimited undo–you can do a lot of stuff and always be able to get back to the way you opened the image. But, once an image is closed, the metadata is updated and you are stuck with the way the image is now unless you reopen and start again.

[DavidB]

Is what you're looking for the "Camera Raw Defaults" selection towards the top of the menu (the one behind the drop-down button at the top-right of the sliders area in ACR)?
The Option-Cancel(Reset) function will reset the image back to the way the settings were at the start of THIS editing session, but the "Camera Raw Defaults" selection will go a bit further back...

[JeffKohn]

Anytime you hit 'done' or 'open' in ACR, the current settings are written to the raw file's XMP sidecar and will become the new settings for that file. If you want to save the current settings before experimenting with new ones, you can do so as there is a "Save Settings" command on the menu drop-down at the top right corner of the settings panel. But you have to remember to do that before hand, so it doesn't really help you in this case. If you still have the PSD/TIFF that was opened from the old settings, you can view those settings in the PSD/TIFF metadata to get the ACR settings, and then manually apply those to the raw file.