My friend had problems with touchscreen (they are gone after two reboots) after her sister used her laptop and when I tried to help I didn't find a way to identify /dev/input/* files. One way I've found was to grep in $ dmesg (/var/log/kern.log) but it doesn't work for me.
Does any standard method exist?
You may use the tool lsinput that you can get installing the package input-utils.
sudo apt-get install input-utils
sudo lsinput
I am not an expert on this (just looked a bit when trying to detect if an external mouse is connected, which is quite a treat)... have you tried this?
grep "/dev/input/event" /var/log/Xorg.0.log
there is a lot of info there. And no, I do not think IDs corresponds, I have 11 /dev/input/event# and 13 ID in xinput...
And if you don't have Internet connection:
cat /proc/bus/input/devices | grep "Name\|Handlers"
Source: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/565543