recovering from gnumeric crash using .gsf-save-* file

[j.brush <brush tryonfarm org>]

hello, friends.

gnumeric crashed exporting to .xls after editing a 2.5M file for many hours. 
the .gsf-save-* file in the directory is approcimately the correct size, but
gnumeric considers it an inaccessible file format.  any possibility, pointers to
recover data?

please cc: to personal email address.  

thanks so much!
.brush