While it's a bit surprising the prosecutor did not call you to testify against the guy it's also a bit hard to comment about that much since you did not say what happened in the trial or why he won acquittal. It could be, for example, something occurred to end the trial before the prosecutor got a chance to call you. In any event, it is not a surprise that you weren't allowed to go in to watch the trial. It is pretty common that potential witnesses in the case are excluded from the courtroom so that their testimony will not be affected by the testimony of other witnesses in the case. For example, the idea is to prevent witness Amy from altering her testimony based on what witness Officer Bob says.
Your lawyer is correct that the verdict in this criminal/infraction case does not adversely affect your personal injury case. However, it is important to know what testimony various witnesses (if there were any) gave in that trial as that could be significant in planning the civil case. As an aside, your lawyer is obviously not your "defense lawyer" as you are not the defendant in the civil case. You are the plaintiff.