If I remember correctly, you were going to ship first and he would ship upon receipt of the amp, right? It's kinda lame that he hasn't shipped yet if he received the amp, but maybe he wants to test it out to make sure it's working correctly. I know when I get a new amp sometimes it takes me a couple of days to move stuff around in the trunk, cut new wire, etc..etc.. before I can test it. Give him a chance to respond and you two can figure out a deadline for shipment. If you don't receive shipping info or whatever on that day start a thread in the "Buyer/Seller/Trader BEWARE!" section and it can be sorted out from there.
I don't know him, but from what I can tell he seems like a good guy. I wouldn't jump to conclusions just yet.
edit: you replied while I was typing the above response, lol. FedEx will technically ship AGM batteries, but if the FedEx is an independently owned "branch" location they either may not know the guidelines or just don't want the hassle.