After EFOs found by chance, today original covers that post administrations create without being asked. And always : it's when you don't look for that you find.
End of June 2006, I read an article by French Polynesia philatelist Christian Beslu about missent letters, published in Timbres magazine #70 (the link directs you to the on-line articles in French, including this one). These covers journeyed through surprising places outside the regular path, and received a mark at the office to explain the delay : « MISSENT TO » and the name of the country.
During a journey with his sino-vietnamese parents, a French friend sent me one letter from Macau, one from Hong Kong and a third from the People's Republic of China. Before leaving, when I brief him on philatelic matter, I showed him the article. He makes fun by saying that one of the three could have the mark. With my luck, no chance !
Late August, after a small number of days of postal travel, arrived the letter of Macau, then of China... but nothing from Hong Kong, who letter has got a 2002 definitve stamp of 3 dollars bearing a security perforation on the right and left side (the one on the left is visible on the scan above). And all his friends received quickly their HK letters. Doubt entered my mind...
Conclusion : early September, I had got a missend letter to Philippines while moving from Hong Kong to Paris. « CMEC » stands for « Central Mail Exchange Center », in Pasay City (Manilla).
Why Philippines... I haven't find yet.