The National Benefit Authority interview questions

After 2 rounds of interview I was offered the job. They sent me my Offer of Employment. When I signed the agreement and replied back with necessary documents including my bank direct deposit info and criminal record check, I received an email from them after 3 days saying they have found another applicant in place of me and so they will not move forward with my application. All this after I had acknowledged the offer of agreement. This disappointed and shocked me a lot.