/etc/sane.d/hp.conf is in libsane-common 1.0.27-1~experimental3ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Uncomment the following if you have "Error during device I/O" on SCSI
# option dumb-read
#
# The usual place for a SCSI-scanner on Linux
/dev/scanner
#
# USB-scanners supported by the hp-backend
# HP ScanJet 4100C
usb 0x03f0 0x0101
# HP ScanJet 5200C
usb 0x03f0 0x0401
# HP ScanJet 62X0C
usb 0x03f0 0x0201
# HP ScanJet 63X0C
usb 0x03f0 0x0601
#
# Uncomment the following if your scanner is connected by USB,
# but you are not using libusb
# /dev/usb/scanner0
# option connect-device
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