The hit is probable cause for a search under the circumstances; it is not evidence beyond a reasonable doubt (not at this time, with only the "hit" as evidence) that there was a death or that if there was the death was recent.
That's an older home in an older neighborhood. It is possible a former occupant died in the home (as my mother died in hers) and there are remnant traces of cadaverine, etc. from fluids leaking into the floor, subfloor, joist spaces, drywall, etc. My mother died next to her bed following a stroke and wasn't immediately discovered.
That's possibility a.
There are others: a home birth in that room, pregnancy loss, menstrual fluids, bloody show - any decaying human blood product or tissue could produce a scent resulting in a hit.
There is even the possibility of a false hit - in good or bad faith - resulting from an improperly used or improperly trained dog.
Analysis to followup and a history of events in the home is necessary to determine the source of the hit. It rules in the possibility that Lisa died there, but it does not rule out other possiblities.
THe extensive search I think was partly to determine if that hit was really related to a recent loss of life.
