Recover data after badblock -w?
Solution 1:
Using badblocks with option -w performs a write test on each block of your harddisk. Once it is finished all block will be overwritten by the test data. These data can not be recovered (even forensic tools may fail there).
Only if you had interrupted the write process before it was finished you may have a small chance to recover remnants of your data that have not been overwritten yet.
Option -w was designed to test new harddisks where data loss is not an issue for write failures.