Police can be pretty good when they are called to the scene of an ongoing incident. You can count on them to settle things down one way or another and make an immediate arrest. But whenever someone walks in the way you did and doesn't appear to be in immediate trouble, they don't like making work for themselves. They'll put your matter on the back burner and maybe never get around to it. That's not the way it should be, of course, but it's the way it frequently is.
The other problem with your matter is that the person you're complaining about is a business partner who owes you money. Sometimes the police will just shrug that off because they see it as a civil matter. And in fact you can
take this person to civil or small claims court
to get your money back on the facts that you're giving.
Things work differently in some states than in others, but I generally advise people here that if you want to prosecute someone, it frequently pays to bypass the police and take your proof directly to the DA's office, ask to speak to an assistant prosecutor and tell them that you want to press charges. DAs have an obligation to all the people in a county, and in most places, they won't send you immediately away, nor will you need an appointment.
That said, DAs are very busy people, and they do not take on every case just because someone comes to them with a claim that they want prosecuted. DAs have the complete discretion to determine for themselves what cases they wish to prosecute and just how aggressively they want to do it. Very frequently they too will tell you that they believe your matter is more suitable for civil court. You can file there on fraud claims and get your money back and damages too, and additionally, the burden of proof is more favorable to you in civil court than in criminal
. In civil court, a jury only has to find it more likely than not that the defendant cheated you out of money without your permission or authority in order for you to win. But in criminal court, in order for you to get your partner convicted, the DA would have to prove its case against him beyond a reasonable doubt. So if a jury believed even a little bit the you two were in business together and he just might have had the authority to use the equipment he did, you lose.
The whole story in a nutshell may be that the DA doesn't really want to prosecute your matter, but it's being handled badly and you're getting a runaround. If it turns out that you do have to bring a civil suit, you certainly don't want the statute of limitations to run out while you wait for a call back from the DA which looks like it may never come. It's time, I think to go over there and see if you can talk directly to a prosecutor. Bring another copy of your paperwork so that there's no excuse this time. And good luck!