Well, there is no requirement that a witness show up at a pre-trial hearing. So this is not a basis for dismissal. Now, if you mean that the victim did not show up at the preliminary hearing, that is slightly different. The the DA could still try to make the case based on police officer hearsay under Proposition 115.
You really need to talk about this with your lawyer on the case. Talk to the lawyer and good luck!
This is not legal advice. In order to get legal advice, you need to retain a lawyer and establish an attorney client relationship. So, talk to your lawyer!
Many defendants have the mistaken belief that a witness/complaining witness/victim must show up at each court date. However, for a misdemeanor case, they are not required to show up until the actual trial dates. (On rare occasions they may testify at a hearing on a date that was set before trial.) So if you are charged with a misdemeanor, then this doesn't give you any dismissal rights.
If this is a felony case, and the witness didn't show up at the "Preliminary Hearing" date, and the witness's testimony is essential to "prove up" the case (to show there is enough evidence to take the case to trial), then this is relevant to your dismissal rights. You have a right to a timely preliminary hearing, and they have a certain amount of days to find the witness and hold the preliminary hearing (assuming you haven't waived your speedy trial rights).
As noted above though, this should certainly be something that you discuss with your attorney.
And be careful not to contact the witness, particularly for the purposes of telling them not to show up to court - it is a crime to do so and way too often individuals end up with an additional charge for doing so.
A pretrial hearing is a hearing where your attorney can speak with the DA ;about their position on the matter; possible resolution; need for more time or discovery, There is absolutely no requirement that the complaining witness show up at this hearing. You should never contact a witness as this could lead to significant charges. Let your attorney do their job.