How do I re-enable an sudo lecture, once it's been seen

I have sudo set to show the usual lecture on its first use by a user. Without thinking, I accidentally triggered its display for a new user as I was setting them up, and now it's been shown, they won't get to see it again.

How does sudo know that a user has invoked it once before? I'd like to reset that so that this user will see the message first time they use it. I don't want to set it so that the lecture appears on every invocation - once is enough - I'd just like sudo to forget that it's already been shown once.

Any ideas how I do that?

On Debian, a user's first use of sudo will create a directory under /var/run/sudo/. The directory is named "username", where "username" is the name of the user which ran sudo.

Removing [or renaming] this directory will cause the lecture to be displayed upon next use of sudo, as well as recreate the directory.

For example, the directory for my user account would be /var/run/sudo/jscott.