Can you give us the full 1901 census record, please? Is this him?
Lansallos:
Frederick W Pearce, 31, b. Pelynt
Bertha, 28, b. Pelynt
Frederick W, 0, b. Lansallos
If it is, he was Frederick William Pearce m. Bertha Rowe in 1898.
www.historicaldirectories.org shows Frederick Pearce, miller (water) Tresquite Mill in 1902. By 1906 John Langmaid was there and Frederick doesn't show in Lansallos at all, and I can't find him as a miller anywhere else. So the move happened between 1902 and 1906 - if you could get hold of directories for the intervening years, you could pin down exactly when he moved.
Have you managed to track any of his siblings (if he had them?). You might find that he followed one of them. Trying to look for the death of the parents also might give clues as to where the children ended up. (Particularly if his parents had less common names - there are a lot of Frederick William Pearces about).