Well my facility is a bit more structured than yours so while I don't have the same dead end you hit, this still is common place with "select MD's".
Next course of action is the charge, then we have a house supervisor. After I've called 3 times, 15 minutes apart... my last call is to the service... "this is a stat call, I've not heard back.. do you have any suggestions or back road to get any doctor from the group to answer the call?" Sometimes the service knows the docs and knows who to call because that particular doc is notorious for that, so just ask.
With no house supervisor to clear your next move, I have called the police to their house to knock on the door. We now require the house soup, but prior to that, I've already put my license on the line, documented my behind off, and dang well going to hunt this golfer, movie goer, function attending arse down.
So next line of action is to assume that there is either ill will affecting him and call the cops or it must be a medical emergency, and call the cops.
Word spreads in the doctors lounge... "did you know I blew off three calls and the cops showed up at my door?" some crazy nurse called them.
I promise, promise once you get that ok, it won't happen again and the other docs will have you on speed dial.
If your snarky, fill out an incident report to risk management, we've had a select few loose their admitting rights for 30 days. We don't play that game.