How to select only photos with metadata conflicts

Is there a way to select only those photos with metadata conflicts? Background: I have a folder with several thousand images in it. Some of them were modified with another application and updated XMP files. I'd like to load the metadata from those files into Lightroom. It's fairly straightforward to do it one image at a time. However, I'd like to do them all at once. If I select all photos and then upload from files, those photos with no XMP sidecards lose all their settings. I definitely don't want that. I want to update from files only if the files actually exist. I'm actually a bit surprised that Lightroom deletes existing settings if the XMP file does not exist.