If you adopt away enough caches so that your number of placed caches is below the threshold for a certain level of the cache owner badge, then you won't have earned that badge. Similarly, if you adopt caches from someone else, you have suddenly placed more caches and earned more FP.
This is true for all badges: they operate on how the database looks when the statistics are generated. Let's say you have logged 1800 caches of the small size and get the diamond badge for that. Then one day, the cache owner of one of these 1800 caches replaces the cache but for some reason places a micro container instead and (correctly) updates the cache size to reflect this. This will mean that you have only logged 1799 small caches, and will revert back to emerald level. This is true for most if not all badges; they can change level (both up and down!) due to events outside your control.