Recently gone through a similar experience with mine. Belt allegedly changed at 72k by dealer selling to the previous owner. I then bought privately at 86k (car now at 96k). Was due for aux belt anyway (which came off in a terrible state, so I'm skeptical it was done at 72k, which then made me question the cambelt). Of course if you're a dealer and selling a car with a 3 month warranty, what are the odds you take the risk that it lasts that long and tell the new owner it's been changed....
So both belts now done, and peace of mind for a few more miles/years.