Some companies don't post jobs because it's easier to search for applicants before broadcasting a job's availability. By searching for you rather than letting you search for them, companies can avoid getting deluged with applications from job seekers who aren't qualified. Search for variations of your job title. At your last job you may have been known as a product manager, but you'll find similar positions listed under project manager. Software programmer positions may be posted as software engineer jobs.
Companies sometimes refer to assistants as coordinators.
Do your research on new and current industry terms and make sure you cover all these variations in your search. Search local job sites too. Some recruiters prefer them to the gargantuan national boards. And check the job pages of companies that interest you. The more places you look, the more likely you are to find the job you're looking for.