To find such a control, I only had to do as I do everywhere else such as:

                    ' Find the LiteralSave control
                    loLiteral = oProcess.oPage.FindControl("LiteralSave")

                    ' If we have found it
                    If Not loLiteral Is Nothing Then
                        oProcess.lToolbar = True

                        ' If we use the default class
                        If cToolbarClass = "Toolbar" Then
                            oProcess.lToolbarUseDefaultClass = True
                        End If

                    End If

I don't know why but I was using a generic approach instead of simply using Page.FindControl().