>>I also opened the file in Acrobat, by the way, and there aren’t any layers in the PDF in Acrobat<<
Which Acrobat did you run it on? The reader or full blown Acrobat?
Why did they scan it as an OCR instead of an image file?
I opened it in Acrobat 7.0 Professional, which is what they called the full-blown version back when I got it.
Why did they scan it as an OCR instead of an image file?
I think they probably just had that set as the default. Lots of scanning software for large-volume document archiving and management, not just Acrobat, will save the image of the document (for future reference) AND extract the text (for later searching). From a company that makes such software:
A text searchable PDF is a PDF file that contains an invisible machine-editable text overlay that allows the user to search for and locate specific text within the PDF document. This invisible layer of text is necessary for a text searchable PDF since the visible text contained within PDF files is not recognized by computers as text. The software used to create text searchable PDF files is called OCR.That's probably just the option they already had turned on. I have no idea what happens when you open such a PDF in Illustrator--it's not something that would be standard procedure. But the idea that the OCR component's text boxes would show up doesn't sound unlikely.