Hey Curtis,
Let's talk through this. Make sure I follow your feedback.
All your RMA(s) will pull up using the "Advanced Filter" option in Case Management. This is easiest way to see the entire list.
In terms of the list view, there is a Case Management Hierarchy to keep in mind on the new portal. I've illustrated the relationship below.
If you do search for the RMA Number directly, it will show as a case and lose the hierarchy to it's parent case. This is a temporary situation that is slated to be fixed in the future and may explain your experience here. Is that what happened?