Peirce’s classification of veritable signs (icon, index, symbol) is not enough to discuss how representamens may relate to ‘real’ objects. Namely, it is said that a fossilized footprint is an actual index of the dinosaur that caused it, because it reveals a natural spatiotemporal copresence, even if the dinosaur does not physically exist anymore. This raises the question whether indexes may represent (dynamical) objects that are not materially ‘out there’, but also virtually possible or habitually necessary. With such a premise, I will resume Peirce’s 1908’s account of semiosis as an hexadic sequence, the correlates of which may belong to any of three ontological universes: “Possibles” (e.g. ideas), “Existents” (e.g. things and facts), and “Necessitants” (e.g. habits and laws) (EP2: 478-479). These three modalities of being are said to supersede Firstness, Secondness, and Thirdness (Jappy 2020: 116-121), because they ground semiosis with multimodal levels of reality that go beyond the phaneron’s subjective experience. Dicisigns (a logical assertion expressing a belief structure with either truth or false values) and sinsigns (an individual existent item, or an actual event which is itself a sign), will also be re-examined. The above will be discussed vis-à-vis examples coming from studies on Episodic Memory or ‘autobiographical memory’, a neurocognitive system responsible for our long-term recollection of lived events (Tulving 2005). Namely, the concept of indexicality will be applied to the typology of memory errors or ‘misremembering’ proposed within the Simulation Theory of memory (Michaelian 2016: 1).