14.04 - Unable to get touchscreen to work on Lenovo Flex 3

I have a Lenovo Flex 3 laptop, which has a touchscreen. I have it dual-booting Windows 10 (OEM) and Ubuntu 14.04.3 LTS. On Windows the touchscreen works fine. On Ubuntu, however it does not work, even after following the official guide. The output of lsusb is:

Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 005: ID 0bda:0129 Realtek Semiconductor Corp. RTS5129 Card Reader Controller
Bus 001 Device 004: ID 8087:07dc Intel Corp.
Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 002: ID 0bda:57c5 Realtek Semiconductor Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

No reference to a touchscreen.
It then asks me to screen ttyS*:

duncan@K7DXS-Laptop:~$ screen /dev/ttyS0
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS1
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS2
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS3
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS4
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS5
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS6
[screen is terminating]
...
duncan@K7DXS-Laptop:~$ screen /dev/ttyS30
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS31
[screen is terminating]
duncan@K7DXS-Laptop:~$ screen /dev/ttyS32
[screen is terminating]
duncan@K7DXS-Laptop:~$

/dev/ttyS33 does not exist.
There is no other connection method listed.
How do I get the touchscreen to work?

I was never able to get it to work on that version. I've upgraded to 15.10 and it works out of the box.