Sites like Trulia.com do not always display current/up-to-date information. Most likely, the owner just has not manually updated all the sites where the property was advertised. And unless your lease agreement states otherwise, the owner of your rented property is allowed to sell the property and your unless your lease states otherwise, your lease is required to be honored by the new owner.
Some agents are slow to update their information, it's not fair and can be frustrating to clients like yourself. That's why picking the right agent plays a big part in how smoothly your transaction goes.
"Simplifying your Real Estate Needs"
Michael Harper - Realtor
Tierra Antigua Realty
Hope this helps,