Thanks for the comments. I don't have explicit travel insurance, but did pay for the ticket with Chase Sapphire which does offer mishandled baggage insurance.
I'm back at the airport now, but learned the bag still hasn't been tracked down anywhere (was last scanned during check-in at CDG). The next flight in from LHR is landing now, so I suppose I'll stick around and see if the bag was on it. If not, I'm going with the suggestion to drive down to Carnoustie and just rent some clubs.
Question: what's reasonable in terms of getting some clothes? I don't want a fight with BA when it comes to reimbursements, but I'm imagining it will cost about 200 pounds for shoes, slacks, shirt and socks, plus another 40 pounds or so for the club rentals.