Newbie to this Civil Service/ Stat Board thread.

I applied to a SB, interviewed 2 rounds, Reference check done. Last Thursday, HR asked for payslip to discuss pay this week so I sent on last Friday.

Now that I have read through pages of this thread, I panic liao.
Can u-turn,
Can they check with a company that I left recently, not on good terms and v short working period, for reference or not? I didn't give them any referral from that company.
Will they go MIA?

I panic like crazy. Have been looking for a job for a long time. Mid-career here btw.