It sounds as if someone did attempt to scam you. It looks like they tried to make $300 bucks off the deal and send the amp right back to you. This unfortunately happens in the online world. There are a whole host of unscrupulous people out there. I once had someone purchase a basically brand new Music Man Majesty off of me then claim that it had "neck issues". He sent me a video which in hindsight did appear curious in that he only showed the face of a tuner as he plucked an open string then fretted a note and showed the note as going sharp. Later I realized that he was merely pressing down on the back of the tremolo to cause the note to go sharp, but that was out of view of the video. At any rate, I refunded his purchase, he shipped the guitar back to me and I checked it out as soon as it arrived and it was absolutely fine. I sold it later to someone who was more than happy with it. I learned from this and am extremely cautious now. If any potential buyer asks for anything outside the norm, communicating off site via email, odd shipping requests, etc. I just move on.