How do I remove keyboards from Lock Screen?

When I tap the keyboard button (globe icon) on the lock screen, it toggles between Greek, Spanish and US English keyboards. Anywhere else, that button (well, the corresponding button) toggles between US English and Emoji. I don't have either the Greek or Spanish keyboards loaded, meaning Settings>Keyboards shows only English(US) and Emoji keyboards have been added.

I'm pretty sure the reason this happens is that I had at one time added the Greek keyboard, and at another time added the Spanish. If I had set an alphanumeric passcode on my phone while those keyboards were added, and used a character in, say, Greek, I would need the Greek keyboard available to me when I'm on the lock screen, or I won't be able to unlock my phone the next time I restart it. But I know that my password (please tell no one this) can be typed using only the English(US) keyboard, how do I tell my phone this???

As I type this it occurs to me that maybe switching to a numeric passcode and then switching back to alphanumeric (with no additional added keyboards) might fix this, I'll let you know.