The loan on the original car was secured by the title of the vehicle. When it was stolen, your insurance company should have paid the value of the vehicle first to the lender then any remaining money should go to the owner. If the owner is "upside-down" in the vehicle he/she will be required to pay off the remainder of the note at that time or make arrangements to pay it off. No, the loan cannot be applied to another vehicle. A new loan must be negotiated.
You will still owe the money even if stolen. Your insurance carrier may give you a check for the difference of what you owe, minus the deductible and the fair market value. It never is equal to what the car was worth though. It is better to keep the car from being stolen. If you have bought the car from a car dealer they will be reimburse you however seek advice from your local citizens advice bureau. If the car was bought privately you will still be liable for the repayments however you should seek legal advice.
There are situations where this is possible. The one that stands out is this: Your car was stolen. You stopped making payments on it thinking, "I don't have it anymore, so I don't need to pay for it." You turned in the report to the insurance company and they paid out, but you did not pay the lender off. Or, you did not have insurance or failed to turn in the claim, so received no money. In the mean time, the lender puts the vehicle up for repossession because you have defaulted. When you are contacted you tell the lender or repo agency the car was stolen, and continue thinking it is not your problem. The lender does not really want the car, they want the money you contracted to pay, so they sue you. You continue to refuse to pay, so the lender attaches your checking account. Yes, they can do this.
A money order comes with 2 parts. The top part you send to the company/person that you are sending the money. The second part is your receipt and you should be able to take that to the place where you bought the money order and get a new one. Look at the fine print on your receipt to see what the process is for a lost/stolen money order.
You get charged with possession of a stolen vehicle I believe. If you knew it was stolen when you bought it then you are handling stolen goods (or a similarly fragrant nosegay of legalspeak, depending where you live) and the police will be keeping a close eye on you and they will be very interested in you. If you did not know it was stolen, then the motorcycle will be confiscated and searched so they can try and find out who had stolen it and where it came from. How you then get your money back, if at all, depends again on where you live.