The patent document says that the patent was assigned to some company. But USPTO's patent assignment database shows that there is no such assignment. My theory is that the applicant/owner didn't report the assignment to USPTO, but inlcluded the information in the patent application. What do you think?
There is no requirement to record assignments with USPTO. The assignee information on the face of the patent is taken directly from the form the applicant sends back with the issue fee payment.