Thank you!
I'd been using the case number in the "Non-immigrant visa" and getting the "your case doesn't exist" response.
Just tried it again using the AA# number as you suggested, and this time I get a "Application Received" notice.
I think that's exactly what we want. It means they've finally moved us from the Immigrant Division to the Non-Immigrant Division, and are getting ready to issue the visa.
Thanks again!
After ours was in Administrative Processing, ours disappeared too. After doing research, instead of using the MNL# in immigrant visa, use your AA# in non-immigrant visa.