No, people clean out their favorites all the time for different reasons. Some people realize they aren't going to buy it, so why keep it on their list? Or they favorited it to look at it later or show it to someone else.
I wouldn't take it personally. Imagine that it's like walking around in a store with an item in your basket and after some thought you put it back. Even I clean out my favorites after a while... there's no way I can buy 80 pages worth of stuff even if I wanted to!