Any time you bring a single-page
image format like .jpg, .png, or single page .tif into Grooper manually via copy/paste,
it will treat the object just as a page. Page Objects in Grooper can not have links
associated with them, so the data you are looking for would not be available.
But if you actually use import the files into a batch using a Grooper Import Provider
like Batch -> New From File System, every file (even single page image
files) should come in as a linked object.