Hi eric,
Please try the following and see if you still have the same issue.
Open new session of Dashboards and login to SAP platform again through dashboards to confirm if you still don't see the query.
Check with Basis to see if the user credentials used in the OLAP connection have access to the BEx query you wish to access.
Try and create new OLAP connection and see if you are able to access the query from this OLAP connection.
Let me know if any of these helped.
Thanks
Mallik