Hi,
Unfortunately, there isn't a
ValueTrack parameter that will give you the ID of the location extension that appeared with your ad. The
{placement} parameter does not provide information about location extensions. Instead,
it shows:
The content site where your ad was clicked (for keyword-targeted campaigns), or the matching placement targeting criteria for the site where your ad was clicked (for placement-targeted campaigns)
In other words, it the site on which your ad displayed.
You could include the {feeditemid} parameter, but that will only contain the ID of the location extension feed item if it was clicked.
Thanks,
Josh, AdWords API Team