I feel bad for you, and that totally sucks!
Unfortunately, you can't recreate the info from a FSEQ file. It is one-way and only in binary now.
You can probably rebuild your setup section of xLights from going to each of the controllers and manually entering it back into xLights. Otherwise, I think you have to start from scratch. Depending on the state you were in when it happened, you could just roll-on with the sequences you have, and create new ones... not worrying about the old ones?
Also, don't forget about all the community provided sequences, that can help get you going quickly!