Your mortgage holder needs to file a release with the recorders office. You are supposed to get the original, recorded, release document back. Often mortgage companies fail to file the proper release. The fact that you never got anything back from them seems to indicate that this might be the case.
I'd strongly suggest you make a visit to your county recorder's office and find out if the release was filed. If not you need to contact your mortgage company and get them to file the release.