The dialog that appears when I press Alt+F2 froze (what is it called? minicli?), I then proceeded to kill it by clicking it after running the command xkill, this was the message:

xkill: killing creator of resource 0x240017b

I then tried restarting plasma-desktop:

killall plasma-desktop

plasma-desktop

Thought this seemed to correctly restart the desktop, it didn't solve the problem since Alt+F2 doesn't launch the launcher.