I completed the campaign, ie completed a trip around the world. Then I started a new campaign in order to gather all remaining collectibles. This has gone fine with all countries except those with several travel destinations which I already visited earlier (and which I have now visited again), such as the US and Japan. Now, I have completed all the cities in the US and Japan and completed all three levels per city, nevertheless not all collectibles show up in my collection. I think this may be due to I visiting them in a different order and I receiving the more "basic" ones, such as flags and internet domain, so I have only 32 out of 45 cards in the US and 6 out of 9 in Japan.

This would perhaps be worth the while looking into. And obviously I would be very happy if I could get back the lost cards!