Not quite...
the auditors that we hired did a bad job and didn't find evidence of bad practices but have admitted they did a bad job
Not quite.
Deloitte were hired by Autonomy as their auditors. The only way they were hired by HP is in the sense that after HP had bought Autonomy, they had been the auditors of that company up to that point and so had a historical responsibility for previous audit opinions. This is why HP sued itself initially (as per the article) and then its former-Autonomy wing sued Deloitte, since HP itself had not directly paid Deloitte for the work, but its acquisiton had.
KPMG were hired by HP for the due diligence in the Autonomy acquisition and wrote the draft reports that was never finalised and went unread anyway by the CEO. KPMGs report is not under dispute.