Possibly. It would largely depend on what kind of surface the blood was deposited on.
For example, I too had an injury in the past year that produced a lot of blood inside a residence. Actually it was a trail from outside to inside, which may help explain even further.
In my situation; there was blood deposited on grass, then on dirt, then on cement, then on sealed hardwood floors, then on tile, then on a towel, then on stainless steel.
We cleaned everything up, of course- but certain surfaces retain HR scent particles (such as blood) much longer than others. The concrete, for example. Scrubbed it with bleach and can't see a thing. But one of our HRD dogs will still hit on it if we put him to work.
The tile? Scrubbed that too- but the grout retains the scent. He'll hit on that also. The sealed hardwood floors- no. The towel we threw away, so I've no idea, lol. If we hadn't thrown it away, I guarantee he'd be hitting on that. The stainless steel- no. But that's because it is a sink, and not a sealed stainless steel container.
Does that make any sense?