You should have kept it. When my kids were younger and we would go shopping and the cashiers couldn't do simple math and make correct change or for that matter even put in the correct price I would correct them.(almost never in my favor) My kids would ask why and I would tell them it was the right thing to do. Eventually I got tired of doing it and one day my son had saved up 250 and was buying a skate board, at 10 yrs old he could do the math in his head. The guy in the shop miscalculated in my kids favor by 75 bucks, my kid said the price is wrong. At that point I said screw it and take your discounted board. If he cant do simple math at 18 and a 10 yr old can they deserve the loss. Maybe if buddy who gave you the tv lost his job he wouldn't be so careless at his next job and the other current employees would have a greater sense of accountability.