Call and ask to speak with a customer service representative. Alternatively, file a Freedom of Information Act Request.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.
USCIS Check my case status is not a full proof. I have seen numerous errors in their system that has alarmed clients. If your employer has confirmed that they did not request a withdrawal of the I-140 and USCIS customer service has verified this then I would not worry too much about what the online system says. it is also important to note the USCIS will probably not talk to you if you call or set up an info pass because the I-140 petition belongs to the employer not the beneficiary and they will kindly ask for an authorized representative of the company or attorney for the company.
You cannot make sure. It seems that your employer is not telling you the truth. Alternative, USCIS system contains an error but it is not very likely with the withdrawal request.
NYC EXPERIENCED IMMIGRATION ATTORNEYS www.myattorneyusa.com; email: email@example.com; Phone: (866) 456-8654; Fax: 212-964-0440; Cell: 212-202-0325. The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter.