Thank you very much for responding and offering to help. It is much appreciated!!
In the "Trees" box in the upper right corner of Family Tree Maker, the old file from 2011 was there, but several trees created in 2012 had vanished.
The missing trees were also missing from the .ftw files.
Following your suggestion I looked in *.ftm and the files appear to be there but they are no longer in the Trees menu. I shall try to "revive" them.