My question involves criminal law for the state of: Virginia

Hi, a couple weeks ago I bought a $120 alarm clock from a major retail store. My friend actually had a similar alarm clock (similar as in the alarm clock is the exact same except the LED light was different colors. For example, what I bought was model AB1234 and the one my friend had was AB1235 - a slightly better model). He gave me his since he already had an IPOD docking alarm clock that he got for xmas and rarely used his. At first seeing mine, he actually said it was the same because when unplugged, you can't tell the difference. Now, with two alarm clocks sitting on my desk, I accidently grabbed the wrong one and packaged it into the purchased box to return. I had paid for it was my credit card and even charged it back to my credit card even though I had the option of getting cash back. I had the receipts. The one my friend gave me was also pretty new and since he didn't use it, it looked new. It wasn't until the next day that my friend stopped by and noticed that the alarm clock on my desk had a different LED color than his had. I never plugged is in so I didn't know there was a difference to begin with. He mentioned it to me and we realized that I returned the wrong one. At first I didn't think much of it except "oops". But I work with a lot of information technology with barcodes, serial numbers, RFID, etc. In bed, I started thinking about it and how (with my background with a law course back in school) this would be interpreted as return fraud. The alarm clocks had UPC and serial numbers so I believe it can be tracked to my exact transaction which has my credit card info, thus, all my personal info. I went back the next day with the correct alarm clock (now out of the box since I already returned that with the incorrect one) to explain my situation to customer service. The cust. svc. rep told me that it was gone. They ship out returns to their warehouse every night. Losing the alarm clock was one thing, but I'm afraid of being charged with return theft for a stupid careless mistake. In fact, she asked me if I wanted to return the correct one. I've already returned and got money for the wrong one, I don't want to double up! With my background and understanding of the technological field (serial number tracking, etc.) and what return fraud is, I wouldn't dare risk my entire life and career for $20! I'm fairly confident that if they wanted to, they could track me down. What do you think the chances are for $20? Also, what should I do? Should I continue to pursue and get someone's attention there? Say a manager? If the product was already sent to the warehouse, they'll be able to see that the serial number on the box and the actual product are different. Is there any way out of this stupid situation that resulted out of carelessness that can turn into a crime. Any way to protect myself legally and prove that it was unintentional? I found out that this can be considered a misdemeanor, meaning I'll get fired from my job and never to hold a decent job if things go real bad. Thanks.