Is this an investment scam?

Me and my parents invested into a local company in 2017, it was a 1 on 1 with the “founder/ceo” taking investment into his company/project. We basically gave him x amount of money for x amount of “shares” but all we received was a printed letter with the company’s logo. It’s a letter with a LLC company that the person owned saying we invested x amount of money for x amount of shares. He advertised having the patents to a technology that was gonna get big. After investing, we participated in inve