Hello there, cstrader. 

It's possible that these attachments were accidentally detached or removed. Usually, attached files are located in the Attach folder which is in the same location as your company file. If you can't find them there, you can locate these attachments where it was originally saved and manually attach or scan them. 

You can also check this article for more information: QuickBooks Document Center: FAQs and common issue. 

I'm here to help you if you have further questions.