he has to uproot it.
Why the difference? - Jews were not suspected of violating Shabbat, so he who did it was probably a brazen violator who would not try to claim that he did it by mistake. Thus, there was no reason to penalize those who did it by mistake. Shmita was different: too many people regarded it lightly and violated it and would then claim that they did it by mistake; therefore, the Sages decreed that even he who plants a tree on Shmita by mistake must still uproot it.
Continuing with invisible damage, a Kohen who brings a sacrifice can easily ruin it with his thought: if he thinks, while doing the slaughter (shehitah) or while accepting blood, that he plans to eat it at the wrong time, the sacrifice is immediately invalid. This is similar to the cases discussed just above, and the rule is that if he did it on purpose, he is liable to repay the cost of the sacrifice. The Talmud then discusses why we believe the Kohen, who says that he ruined the sacrifice.
Art: Rabbi by Rembrandt Van Rijn