You need to find a backup of your data and locate the following 4 files:

GLACCGRP with a size < 20 KB
GLATREE with a size < 200 KB
GLRPTGRP with a size < 20 KB
GLRPTTXT with a size < 20 KB

Once backup copies of the files are located use them with a copy of your live data and see if your Statements Groups come back.

Never perform this type of testing with your "production" data!