I'd noticed that once the list has been cleared and rebuilt, the fast scroll appears, I don't know for how long.
Your work around worked on a test project, but for some reason not in the large project I am working on at the moment. Another options is:
Dim PH As Phone
If PH.SdkVersion = 19 Then
Dim JO As JavaObject = ListView1
JO.RunMethod("setFastScrollAlwaysVisible",Array As Object(True))
End If
Not ideal, but it worked for me. I already use the Phone Object within the app so the permissions are already there. May be an issue for some.