Sorry, you are out of luck. Since you have "Remove data from the external date range before saving the workbook" checked the added data was never saved and there is no place to retrieve the user's data from.
To prevent this kind of accident going forward, I would change the workbook to macro enabled(.xlsm), if it isn't already, and add a check in the BeforeSave event to see if the table has been unlinked.
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Dim sMsg As String
' Assuming the data table is the first table on the first worksheet
If .SourceType <> xlSrcRange Then
sMsg = "Any changes you've made to the table won't be saved unless you unlink from the database!" _
& vbCrLf & vbCrLf & "Do you want to unlink?"
If MsgBox(sMsg, vbExclamation + vbYesNo) = vbYes Then