I know nothing about the loan company, and know how cut-throat they can be. But may I mention that Gaurdian Portfolio is contracted as a "last reort" between loan company and client, as I understand it. They come to you not to "strong-arm" you, or repo, but to act as a direct representative between you, and for you, and the company. If he placed a letter and went through your mail, that is wrong.
But if you had talked with him, he would have explained his job, and how he could help you. He would have made his report, explained your intent, and made sure that the "breakdown" in communication between you and the company would have been resolved. Of course you would have had to keep your promise to the "tee" without excuse. But had you done that, you most probably would have your car, and no stress concerning the situation.
Loan companies NEVER make money on a repo. Regardless of what you owe. Most people get a 4 year loan, and thru the whole time the car depreciates. Paperwork, personel etc. eat them up on repos. They are in the loan business, not car sales. Most people that get behind, is in the last 2K of a loan, as the car is old to them, maintainance higher, and they think "have paid for the car, those crooks are getting blue sky". Their business is making money off their money, not making people happy by buying them cars. So a red flag goes up during that time.
Hope you are feeling better and life works out for you.