Serenity was easily pulling in $10-20k per week from his sales. He had stock in a bunch of different things and he's run out in the past without taking a break.
Generally a vendor doesn't stop all business that quickly and just disappear like that. Even though most (if not all) of the stuff he was selling was quasi-legal, I'm willing to bet that someone at the local post office contacted OIG and some serious heat came down on him.
The fact that he still put up a quick notice leads me to suspect he wasn't outright arrested but he probably got wind of an investigation coming down on him. He was probably sending out 100-200 packages a week that was hitting a smaller volume post office.
Unfortunately I think he took on too many clients and he didn't limit the number of orders a client could make per month. He probably should have made a limit of one order per month which would help combine a bunch of smaller weekly orders into one larger monthly order. That would have reduced the volume of packages going out substantially. He also could have stopped taking on new customers and only dealt with his larger volume clients.
Hindsight is 20/20 but I bet something like this played out. It really sucks that this happened to him because he was honestly one of the best, if not the best, vendor I've ever had the pleasure of dealing with. If I had to find some minor issue with dealing with Serenity, it would probably be the local post office sitting on express orders for 1-2 days somewhat frequently -- but that was out of his control.
I should have put in an order earlier and make it a hard rule that if I drop below a certain amount, put in an order quickly. Dealing with ODSMT withdrawals is a mf'er.