Your facts indicate that you were under investigation for an alleged violation of a State charge, and you cite the Federal Rules as if they will apply to the State proceedings. That is not typical, as each State has it's own statutory rules pertaining to the return of seized property. In short, the State can hold your property while it is part of any evidential basis to an on-going investigation. Just because the water is calm on the surface, does not mean that the State is not proceeding with the investigation. Examination of a hard drive is expensive and time-consuming. The State could be continuing the investigative process without you knowing what they are doing, as they are not required to inform you as to the status of their investigation. In representing client's here in NJ, we have seen cases linger for more then several years while the investigation continued and we waited to see if an indictment was going to be issued.
While you can file a Motion for the return of the property, I suggest that you discuss this with a local lawyer who practices criminal defense before you decide whether to file the motion. Good luck.
This information is offered for educational purposes only. It is not intended as legal advice and you should not rely upon it to decide how to resolve this issue. No Attorney-Client relationship is intended or established by this response. You are faced with a situation where you need to consult with an experienced defense lawyer admitted to practice law in your State before you make any decisions as to how to resolve this issue.
My colleague's answer is correct and thorough but I would add that you are not likely to get any property back until the criminal investigation is over. Sometimes that means after a trial and a not guilty verdict. As noted, the FRCP have no applicability in a state law proceeding.