I mean, they might implementsome anti-cheat system that monitors users that always d/c instantly when they get a gem. This can be done in on the servers logs. Look the possible log below. Put yourself in shoes of a GM, will you be suspicious that miner x is botting if you see something like this?
e.g.
Log for "miner x"
1/5/06 13:20:22- Gained a refined rainbowgem
1/5/06 13:20:23- Logged off
1/5/06 15:35:03- Gained a normal phoenixgem
1/5/06 15:35:04- Logged off
1/5/06 19:03:55- Gained a Super dragongem
1/5/06 19:03:56- Logged off
2/5/06 12:00:25- Gained a normal moongem
2/5/06 12:00:26- Logged off
How likely is a non-botter always to d/c within 1 second from when a gem is found?
My suggestion is that if "play a sound when gem is found" is implemented, it will be harder for GM's to check that they were bot-mining because you dont need to d/c when u find a gem so therefore the logs wont show that you d/c straight away when you get a gem.