Unfortunately Trulia is not very up to date. I have had clients send me listings from Trulia and most of them were sold or even yet not even listed. Yes, if there is no house number or MLS ID then it is not listed. The best way to get accurate information is to contact a Realtor that is an expert in the area you want to buy.
Listings on Trulia are as up to date as the sources they are pulled from. Not all agents update their listings after posting them as active. If there is an area you are interested in an agent can pull all active listings from the MLS.
The timeliness of Trulia's listings is at times questionable. If you would like to get the most up to the minute availabilities or closed sales, you should contact a REALTOR. I can set up an automated email notification for you, which you may opt out of at any time. Let me know if I can be of further assistance.