Your code doesn't compile so I don't see how it is finding or not finding anything.
Find whole word is disabled when certain characters are included in the find string. You could do this in steps (just make sure your document is not a thesis on the behavior of the Aardvark):
Code:
Sub InSteps()
Dim oRng As Range
Set oRng = ActiveDocument.Range
With oRng.Find
.Text = "^^"
.Replacement.Text = "Aardvark"
.Execute Replace:=wdReplaceAll
Set oRng = ActiveDocument.Range
.Text = "Aardvarkmb"
.Replacement.Text = "Test"
.MatchWholeWord = True
.Execute Replace:=wdReplaceAll
Set oRng = ActiveDocument.Range
.Text = "Aardvark"
.Replacement.Text = "^^"
.MatchWholeWord = False
.Execute Replace:=wdReplaceAll
End With
End Sub