Much of it depends on why they thought you were on parole - surmise, rumor, told so by presumably knowledgeable authorities, saw your name on old parole folder, saw it on new parole folder? That goes into the good faith hopper, and there is nothing more to add to Scott's answer.

There are two issues here. The first may hinge on whether there was a reasonable belief that you were on parole. The second is whether the police or your parole officer did the search. If either of these issues is in your favor, the marijuana should be suppressed. You should consult a criminal lawyer to assess the facts of your case.