The quote only says that the Kanohi’s shape seems “vaguely familiar” to Matoro, and that scattered nearby was “blue Toa armor.” There are at least two ways this could be interpreted.
This may mean that the mask vaguely resembled one of the Kanohi seen by Matoro in the past – meaning the 12 Kanohi on Mata Nui (including their Great variations worn by the VNRT), the eight Kanohi worn by the Inika/Mahri, the Olisi, the Mask of Adaptation, the Kualsi, and the Noble Kiril.
It may also mean that, deep within Matoro’s suppressed memories of Metru Nui, he recognizes Toa Tuyet as she appeared when she was a member of the Toa Mangai – this is the option that I personally subscribe to, since the shape seems “vaguely familiar.” It hints to the idea that Matoro feels like he’s seen Tuyet’s mask before, but he can’t place where because those memories were locked away by his time in the pod. We see that memory erasure can involve resurfacing memories/deja vu in Karda Nui later, when the Toa Nuva slowly realize they have been there before.
In neither case do I think this involves Matoro recognizing the armor as belonging to a Toa variation he recognizes – the addendum of Toa armor being scattered nearby is completely in the third person and does not invoke Matoro’s point of view like the Kanohi’s description does. This means that the narration is calling to attention the presence of Toa armor for the audience’s sake and that whether or not Matoro recognizes it as such is irrelevant.