That could make it difficult to pursue the possession charge (H&S 11377) unless there was at least a presumptive test done. Do you know if they tested the contents in the field?
Without the dope or a test, chances are all they'll have to pursue is the pipe charge. For that, they can move forward without the object in question in many instances. It depends on how comfortable the DA is with it. I'd be surprised if they went to the mat on this, though. It's likely they are hoping for a deal. Even when these offenses were more serious I don't ever recall going to trial for a pipe offense (H&S 11364).
I know in Michigan we have a judge who is notorious for sentencing drug and alcohol offenders to the maximum allowed, regardless of plea agreements, so criminal defense attorneys in his court recommend to their clients that they ask for a jury trial.
There can be factors other than evidence that will influence the outcome of charges so a defendant really needs to rely on their own attorney for guidance.