Hi,
The Save Selected function could have problems to access hidden / frozen objects. If you want to save it this way, please remove any restrictions from these object(s) / layer(s) or move them to any "unrestricted" layer.
Anyway, we recommend you to proceed a Merge into a new scene with Display Influences and Select Influences selected in Merge window. That will bring to your new scene all objects needed to rebuild the Forest object.
Kind regards,