Could be one of several reasons:
- AW has taken the profile down for a (perceived) violation of rules
- The girl has temporarily suspended it herself - some do this when they go on holiday
It's always a good idea to save favourites in your hot list since when/if the profile comes back it will show in your hot list again.
The hot list is also good for keeping track of girls when they change their name, since it tracks by profile ID number not name