It seems the bad doggie breath I had noticed before leaving had been caused by an abscessed canine tooth. I had requested a tooth cleaning when I brought him in and the problem was discovered then, as he was also not eating and had lost ten pounds since a previous visit.
He is eating fine now, getting antibiotics and seems as chipper as ever. Looking up the function of the upper canine tooth I found it is used to capture and hold prey. Since Baron is fed regularly here at home, I don't believe the loss serious. Well, on second thought, it may reduce the rate of his squirrel captures, but he'll just have to tough it out.