Ubisoft has admitted to a bug that has been erasing stats for The Crew.
To be clear, the bug does not affect major save data, such as level progress, cars, or money. Instead, this affects data such as total miles driven and landmarks visited.
It turns out that the server was unable to load those stats sometimes, and on occasion, was even erasing them. Ubisoft has patched the bug, but they aren’t done fixing the issue completely. As a result, stats stay saved, but they are not get displayed back to you in your game.
Of course, a future patch will address this issue completely, but for now, players who want to see their updated stats need to log off and log back into the game several times. No word as well if deleted stat data can or will be returned in the future.