How to use a White Scroll?

Oh really? Ryan lied to me haha. He told me he was scrolling stuff and it used his white scrolls without warning.

Might be that it sometimes does and sometimes doesn't?
A buddy told me one of his white scrolls disappeared, but he doesn't know when or why. (It's a shared account, tho, so his partner might have used it, intentionally or not)
To be safe, I wouldn't have any white scrolls in inventory unless you intend to use them just then.