Mac OS X Sierra 10.12.2 finally fixed the problem with my HP PhotoSmart 2570 scanner not appearing in the Image Capture application.  This problem started happening sometime after applying a security fix to Sierra. Reference issue http://h30434.www3.hp.com/t5/Scanning-Faxing-and-Copying/Scanning-not-working-with-Mac-OSX-Sierra/m-p/5918250#M158514

After I updated to 10.12.2, then deleted and re-added the Photosmart 2570 series (Kind = Bonjour Multifunction) printer, the printer now appears as both a "Print" and "Scan" device in the Printers & Scanners panel, appears as a Shared scan device in the Image Capture application, and properly scans. Yay!