Product not received - radio silence from seller

if a honest vendor and if he ship with tracking they will help you even of you let auto finalize

but nowadays markets are full of selective scammers

by selective scammers what do you mean? that they scam sometimes, and sometimes not? or some people and not others?

im in same situation as OP.

They pick and choose who to scam, but it's easy to avoid. Find a vendor that has great reviews on tforum. Order from them.

Next time dispute.

It's a bad sign when this goes down, why work with them again? Short term, order again and don't let it AF, long term find someone else. There is no excuse for a vendor to ghost you when you placed an order that wasn't received, that's bad business especially when they don't reply to messages after an AF. If the market is thin, chalk it up as a "how to" not let my orders AF and try again. How important is it to have this substance and weigh in if you are willing to get scammed again? It's all about risk and reward. Find another competitor that works and if you can't, try again but don't fuck yourself with being laxed.

what would be their criterias? someone who doesn't order often or big quantities for example?

No way to know what they're thinking, and so there's no way to avoid falling prey to a selective scammer except to simply not order from them. There are well established vendors in every category that sell top quality products at great prices. Don't fall into the trap of thinking you're gonna discover the next up and coming vendor before they "get greedy and up their prices". The reality is that the market sets the price for products. If you need recommendations for vendors, you need only ask and people will provide.

The thing that's confusing me is that the messages I've sent haven't even been read, so it's not definite that he knows there's an issue and is choosing not to do anything about it. I'm not sure how DrugHub's GUI works for sellers, do messages about existing orders enter a different inbox from new orders?

I would assume that any message sent you'd get a notification, after multiple messages sent and someone wouldn't even bother to check is pretty lame. If they haven't logged on then that's different. With a vendor you'd expect some level of professionalism. This is the wild west and anything goes, sometimes you score great with good vendors and often you get into involved with questionable interactions. Sounds like a 3/5 vendor, they're great when they don't have their money, bad when they do. In the end, it's all about what you are willing to deal with. Either make another purchase and don't let it FE or move on.

Next time dispute the order, never let any of your order autofinalize.