Tom,
Memory can be affected by many external and internal factors. Blunt force trauma for example would be considered external while the loss of memory do to the lack of brain cells due to excessive use of alcohol would be considered internal.
I do not know your age, however, memory loss can be caused by the onset of Alzheimer's Disease. A low sugar count also comes to mind. So as you can see the problem you seem to have recalling events such as the measurement session noted above can be the result of many different causes and even combinations of said causes. I would suggest that you contact a physician if these symptoms presist.
I've known both Mervyn and Peter for some time now and have never detected any signs of memory loss so I regret that I cannot comment on the state of their mental capabilities regarding memory loss.
As for myself Nick was left with either deeming me an Old Contemptible or simply a Contemptible Old Buzzard as was the popular opinion. The decision was made that Old Contemptible was a shorter title, least I become vain, and there was no chance of invoking the rath of the SBNAS (Save the Buzzards of North America Society) by this decision. You probably know the bird as Cathertes aura.
I hope this answers your question.
Regards
Brian