If you go to this site (Stafford County Real Estate Assessment)
and search by Street Address, you can find that property and some nearby ones (I suspect that's where Trulia gets its information).
Now, once you have selected that property, click on "Transfer" Tab on the right side to see the property transfer history (sales).
You will see the following:
Deed ------------- Sale Price ------ Date ----- Prev Owner -------------------- New Owner
030024342 $319,300.00 6/20/2003 SPEAR BUILDERS OF VIRGINIA INC -----reducted -----
030005987X $451,140.00 2/19/2003 STAFFORD LAKES L C I
990022050 $0.00 10/24/2002 SUBSETUP BY STAFFORD LAKES LC
(I removed the current owners name, although that's really public information - anyone with a computer can look that up).
Sounds like the current owners bought the place for $319K, just like Trulia said, but before that there was a sale for $451K, just like Trulia said.
However, what you said, and I am quoting, [[[The drop occurred while the current sellers owned the house.]]], is not correct.
The previous transfer was between the land owner and builder, I would guess related companies. It appears that a subsidiary of Stafford Lakes LLC initially bought the property (probably land at that time) for $0.00, and then sold what was probably the finished property for $451K, and then the builder sold to the first owner at $319K. I have no idea why they would do this, but I am sure they had very good reasons of their own to do that. I can tell you that in terms of accounting, at least on paper, Stafford Lakes, LC made $451K revenue minus their costs, and Spears Builders made $319 - $451 = $132K loss.
In fact, if you check nearby properties, like 8 Abington Court, they all look to have the same transfer trail.
Your real estate agent, I am sure, has a better explanation than mine why this might have occured.