Hi Crewman,
That is what a National Archives cite for war diaries and similar documents usually looks like, but I can't find a match using their simple search tool here:
http://www.collectionscanada.ca/arch...2010502_e.html
or the advanced one here:
http://www.collectionscanada.ca/arch...2010503_e.html
I tried 10942 as both a file number and as a microfilm number (and a few other combinations as well) with no luck. You may wish to try some other possibilities (especially with possible unit names) in the simple search tool, limiting the search to RG 24. I don't know of a way to search for that file number.
Record Group (RG) 24 is National Defence, where war diaries etc are maintained. That file number, however, doesn't match anything in that group. It does match some unrelated stuff in RG 25 (Foreign Affairs).
Don't know enough NAC history to know if their numbering system could have changed over the years, though it seems unlikely. Could only suggest writing them and asking them if they can track it down.