How to input unicode characters with the phone locked?

I've made the mistake of putting an emoji character (❌) in my unlock pin. This usually works fine, but after the last time I restarted my phone, the two keyboards I have installed on my phone refuse to show the emoji keyboard on the lock screen. This makes it impossible to type in my password :( I've got an external keyboard, but after reading some HID documentation I can't seem to find a way to enter this character. I found some solace with the special charcodes \uef00/\uef01, which would allow me to input something, but they don't seem to work; they're mapped to x+shift+alt and space+capslock, but they don't seem have their intended effect, even on another phone I have lying around (although with \uef01, I see something going on at the bottom of the screen pop up, but it doesn't let me input anything...) Do people have any other suggestions? I don't have USB debugging on :(