Today I tried to connect my phone to my computer with a USB cable and I got three error messages in Dolphin:

The file or folder udi=/org/kde/solid/udev/sys/devices/pci0000:00/0000:00:14.0/usb1/1-3 does not exist.
No storage locations configured
Could not enter folder /samsung phone

I recently paired my phone with KDE connect. Is it possible KDE Connect killed my phone?

Given your details supplied, there can be any number of issues here...
however in another post I suggest using gvfs
also try gmtp ...