I did it through the USPS website, there is a link/section called "where is my package/mail?" that you can use to submit inquiries. I filled out the form and explained my situation. Next day or two someone from my local USPS contacted me and said they would investigate. The e-mail had his e-mail and phone number so I waited for a week and e-mailed him to find out what was going on. I told him my employer was waiting on my EAD card and that I could lose my job. I told him, if ya'll lost it it's no big deal, USCIS will replace it as long as ya'll provide me a letter stating it was lost. So he immediately sent me an e-mail saying it that according to GPS tracking, my mail was delivered at a different location and provided a range of addresses on the same street. That was it.
Then I mailed proof to USCIS service center and now I am just waiting.