A phenomenological 2D model, simulating the martensitic transformation, is built upon existing experimental observations that the size of the formed plates -in direct transformation-decreases as the temperature is lowered; then they transform back in reversed order. As such, if a reverse transformation is incomplete ("arrested"), the subsequent direct one will show anomalously large number of big size plates-old plus newly formed-but consequentially a depletion of intermediate sizes, due to geometrical constraints, phenomenon that generates thermal memory.