There can't be a WIA or TWAIN icon on the machine, that wouldn't be WIA or TWAIN at all, just scan to SMB/FTP.
If either is setup right on the PC, a template will appear in Network Scanning as a template though.
And it can't initialize until after you put the IP of the scanner in the Administrator Options of the driver properties.
As for the successful failures, that is a known issue in older firmwares but not in the one I linked, so if that still happens I suggest calling in to Xerox and reporting it to 2nd level (assuming you have a maintenance agreement)