Is it possible to tell it was that specific type of knife was used from seeing wounds...to the point they can go looking for recent purchases without it being like searching for a needle in a haystack? I guess I was thinking that at most they could tell single vs. double edge...and serrated vs plain edge...and length maybe...but that wounds wouldn't get them enough to know what exact knife to search for?
JMO
If the knife contacts bone and leaves a mark, they will have more information than if it only left a soft tissue wound.
Not enough info to know specific manufacturer or exact model IMO, but they may be able to get into the ballpark of type of blade, and then use that general information when they canvass for recent purchases.
And if they did recover a knife during a search that they suspected was the weapon, they would likely be able to test and either match or eliminate forensically, if cuts on any bones are present. If you are familiar with the trial of Chandler Halderson (who dismembered his parents), there was extensive testimony on the forensic process by which they matched blades from saws, knives, and hatchets in the home to bone cutmarks that is very informative on this issue.