Fired & given my tip money in a sealed envelope in cash. Do I have to pay the overpayment back?

I was fired from a bar after 2 weeks of working there. It was due to my disability but I know that is hard to prove. I came in to get my final paycheck and tips. I went in with my Grandfather who is a retired Portland, Oregon police officer with over 30 years of service. I took him with me as a witness because after being fired, I didn't trust them. I was handed 3 sealed envelopes, all with my name on them bound together with a rubber band by the bar's manager. Envelope #1 had my paycheck in it. Envelope #2 had the personal check I had gave them for my OLCC. Envelope #3 had my tips, in cash, in it. I didn't open the envelopes until after I get home and didn't sign anything upon receiving them. I see that there is more money than I had expected in it but my Grandpa told me that it was probably severance pay. The next day I get this message saying that I need to repay the money I stole before they call the police. Then I get a message from another manager saying they overpaid me in my tip envelope. That I was given all of the tips for the week. A total of $360 more. I find out from another employee that still works there that they called the police on me, the police showed up at the bar, left, and then he heard the owner tell the manager that the police is going to be back in an hour. The police have not been to my door. Only 30 minutes had gone by from the time they texted me about the missing money and the time they called the police. Honestly I wanted to hold onto the money to stress them out for a while so they know how it feels. How long can I hold onto it before any real legal issues and do I have to pay it back at all?