I don't have enough information here to know whether it's a very tough case or not. I can say, however, that if he was found in possession of cocaine, even if there was a violation of his Miranda rights, that doesn't mean much under these circumstances.
The average non-lawyer misunderstands what Miranda stand for and thinks they have a dismissable case if the officer never read them their rights. That's not true, unfortunately. Miranda, while important, has a much more limited holding. It stands only for the proposition that after a defendant has been placed under arrest, he does not have to submit to police interrogation
. He can say that he would rather wait until he has a lawyer, and refuse to answer questions about the incident.
In many cases -- perhaps this one, for all I know -- Miranda warnings never have to be read, because when the police see the crime go down right in front of them, they don't need to bother with interrogation. So Miranda isn't relevant at all in many cases, and when it is, the case won't get dismissed. Instead, if a judge decides at a pre-trial
suppression hearing, that a defendant's Miranda rights have been violated, any statements he made as a result of that violation and/or any confession that he signed would not be admissible at his trial. Other than that, the case goes on with all other evidence intact.
There are other things that may be challengeable. I don't know from your facts why your friend was stopped and the circumstances of the search and the finding of the drug. Perhaps there will be something like that for your friend's lawyer to work with if he wants to try the case. In that instance, if his 4th Amendment rights were violated the drugs couldn't be used against him. No drugs = no drug possession = no case.
On the other hand, if this is a first offense, or at least a first felony offense and a defendant with a fairly clean sheet, he's likely lookiing at nothing worse than felony probation here, and if he has a drug dependency and wants to help himself, he could even wind up in a specialty program like Drug Treatment Court
where, if he completes all court-mandated programs successfully, the case against him can be dismissed.
As to when the police bagged the evidence that may or may not be an issue. If they did something wrong, the state would be unable to show a proper chain of custody and then the drugs would not be admissible as evidence. But it's late in the case that such heariings are calendared, by which time the most favorable deal may be off the table. In any case, it's not precisely when the drugs were bagged, since the officers were out in the field but whether they can establish the chain of custody well enough so that the drugs on the DA's table will be admitted as the same drugs that were in your friend's possession.