Comment # 15 on bug 954215 from Egbert Eich

Ok, so it is a KDE issue.
Point is: when you vt-switch, suspend/resume or do the 'udevadm trigger ..'
command the Xserver will close and reopen the input devices. All devices will
be back to their default settings. The desktop is expected to restore them.

In your case, the desktop disables them. Unfortunately, to the Xserver and to
any user space application it looks like the devices have been unplugged and
(other) devices have been plugged back in. 
There is no way to identify that the new devices are the same ones as the old
as most devices do not bother to sully a serial number.
The only thing a desktop can do is to try to determine if an identical device
(ie model) has been plugged in before and restore the old settings.
I'm not sure how it is done on suspend/resume, but there the issue occurs as
well.

I'm changing the component to KDE Plasma as the KDE folks should look into
this.