score:11
This book, The Papers of Woodrow Wilson, vol 53 in a footnote on page 308 states that on Dec 3, the resolution (S Con Res. 26) was introduced by Senator Sherman to declare the office of President as vacant. So you have another source, with date and resolution number. All I find is a snippet view so can't give you much more.
Upvote:7
Here is the Congressional Record, Volume 57, Pt 1, that includes the records for Dec 3 1918.
The resolution that you're looking for (S Con Res. 26) can be found on page 23.
For an explanation of "Over, under the rule", the US Government Publishing office has this to say. (Which, frankly, is about as clear as mud).