Depending on what kind of title insurance you bought

I always recommend my clients to buy the premium ( or call it advanced, eagle, etc) title insurance so all of your liens are covered.

If you bought the basic title insurance, well, only recorded liens are coverd. Anyway, the title company should always find the recorded liens.

In your case, you should talk with your title company. It is the title company's job to figure out if the previous owner owed anything, especially tax liens, at all.