I just find it interesting that everyone wants to jump to the conclusion that this buyer was a scammer.
That part is simple: When someone sends a perfectly functional item to someone who then claims something is wrong with it, the first two assumptions are either "shipping damage" or "scammer." If the box and external parts of the item are damaged, we know it's shipping. But if no issues on the box, no issues on the outside of the item, then something is up. Yes, something could have been jarred loose in shipping without any external damage. But sellers have ever reason to be leery. If I ship something that works perfectly and you tell me something is wrong with it, it better be something that traces easily to shipping. Tubes jarred loose, etc... If not, I'm not likely to trust your word when I know mine was 100% true and there is a very slim chance that something else happened inside the amp, while in shipping.
I'm trusting by nature, but am quickly learning to adapt to the new breed of online buyer scammers. Read my story about my son in law above. And, a similar thing happened to me EVEN WHEN SELLING LOCALLY on Craigs List. My boy Bodia gave me such a good deal on a Mark V that when I decided to move it along, I figured I'd be splitting a $400-500 profit on it with him, but didn't want to ship it and was only getting trade offers for months on it. Finally got someone offer me just a couple hundred more than I paid Bodia and I took it. A few days later, he called me and said the reverb didn't work and we needed to talk about what to do about it. A freaking Mark V in perfect condition for $1300... and we need to talk about it.... First, I NEVER used the reverb on the amp, as I had a pedal in the loop for that. But a week before I sold it, in one last attempt to make sure I wanted to sell, I went through all the modes again and while in Tweed mode I did turn on and up the reverb and it worked perfectly. His first offer was that he would take it to a tech, and I'd pay the repair bill. No way! I wasn't going to get stuck with a $200 or more bill. I'd buy the amp back. But I didn't want the amp back and had no other buyers. After 3 days of back and forth, he said he'd take $100. I said I'd think about it and still might just take the money back because I knew it would sell online for $1700 or more. I also told him that I knew it worked when it left me, and for the price I sold it to him for, he should considered leaving it as is. He said no, it didn't work the first time he tried it, and so I had misrepresented the amp as 100% working. Two days later, he calls again and says he called a tech and the guy wanted $75 just to look at it, plus parts and $65/hr for any needed fix. He said if I paid him $200, he'd call it good and take it in and pay for the repair himself. I said "no way I'm selling that amp for $1100 total (like Bodia did, and I would have sold it to anyone here for that as well). I had already bought other amps and actually used part of this money for the Atomic AA12 which was on sale, so my play fund was down to $500-$600. I told him I'd give him $100 and no more. 3 days of texts and emails later, I told him I'd give him $150 just to get rid of the guy, and he has a friend meet me to pick up the cash... didn't meet me himself. Needless to say, from the time this started, I simply got more and more and more suspicious. If I hadn't bought the AA12, I would have said "bring it back. $1300 is too cheap and I never should have sold it to you for that even if the verb didn't work."
6 months later, some guys posts a "watch out for this buyer" ad in the music gear for sale section of Craigs List. Saying that he sold him perfectly functioning gear and even after coming way down on the price, the guy bought it and immediately claimed something was wrong... but he'd keep it for a partial refund of payment. When the add ran, 6 other people complained that he had done the same thing to them. Amps, guitars, pedals, etc. Always something is wrong and I'll keep it but give me part of my money back and I'll get it fixed... 2 days later the thread was nuked, but I saw it and it proved I was right all along about him. I'm sure there were others who he got because he buys a lot of gear. Since I still had all his texts, I texted him and asked him if he saw that on Craigs List. I also said "I know that reverb worked right before I sold you the amp. It still worked fine when you got it, didn't it?" Needless to say, he didn't answer.