Medicare pays for skilled nursing home services if they are considered 'restorative', following an inpatient hospital or an acute inpatient rehabilitation stay. The nursing home needs to have a treatment/care plan for him for Medicare purposes since the goal is to help them get back on their feet. (They should have a care plan, of course, under any circumstances).
Who is his next of kin? His spouse or adult child should ask to meet with someone at the facility to understand what the treatment plan is for him, along with your ex-boss, if he is able. They could ask to meet with the physician in charge of his care: patients in nursing homes don't usually get much hands-on physician services in the facility itself but there is a physician responsible their overall care there.
Also, when my mother was in a skilled nursing facility following a stroke, it was the social services department that we had the most day to day interaction with, sometimes at my instigation and sometimes at theirs. They were very helpful. So that's another possibility.