Yes, there was a small drop of Amanda's blood on the faucet, and there is no way of knowing when it was deposited. When Amanda testified that the bathroom had been clean when she left the day of the murder, she didn't mean totally without any drops of any kind. A drop of a person's blood in a bathroom they use every day is not evidence of anything, unless you have a lot more to back it up (which they don't).
This is an argument showing the pro-defense bias. The drop on the faucet was very visible. One may claim that it was small, you may not notice when you enter the bathroom. It's true. But it's not a strong argument. Because when one use the bathroo, at a certain point they would wash their hands, use the water tap and put their hands under the water flow. During this movement, you would look at the water tap at a certain point. It's a very attention grabbing point, a focus of visual attention.
It is possible, in rerum natura, that a blood spot is left there for days unnoticed. But it is not likely. Not by both Amanda and Meredith, especially since Meredith was reported to have been particularly grossed by blood drops in the bathroom. That blood drop wouldn't remain in that visible spot for days after days. It's unrealistic.
But also, another relevant fact is that the blood spot is Knox's blood, not Merediths, and this not only makes it become suspicious and unjustified because of its dating, but also because of its unjustified
origin: because Amanda Knox
fails to explain its origin, so that you talk now about a blood stain the origin of which remains vague and unknown; but in fact since the blood is her, she
must have know exactly its origin
and day.
Then, do not forget the other multiple lies - that is inconsistent, non credible statements - by Amanda Knox that relate to that spot, in her account: first she thinks it is from her ear, then she deems the size of the bathmat stain "too large" to be from her and rules out the idea of being wounded without checking her body, and finally, as I just said above, this fact that she only refers to a vague and unknown origin, whereas realistically she must have known if she had been bleeding in the bathroom, because it'ts not something that goes unnoticed.
Yet, in rerum natura it is still possible for people to hypothesize that the drop may originate from any other day, that the remaining there of the blood was causal and that went unnoticed by Meredith for days by chance, and that vagueness forgetting on the part of Knox's memory is just mistakes.
All this is possible.
But it's not credible, not likely. It's weak.
The blood drop crossed with all these suspicious inconsistencies in statements and circumstances about it, and with the findings of other mixed traces of non diluted blood (cotton swab) and other suspicious mixed DNA traces, is indeed a piece of circumstantial evidence.