In its liquid form, GHB looks like water. It has no smell, and is tasteless or has a slightly salty or solvent taste that can be easily masked
N has a taste and is bitter so easily distinguishable from gab and also has a smell aswell.
liquid N comes in a tamper proof sealed bottle, the whole idea of that is so it can't be tampered with!
then you could buy a testing strip thats tests for ghb, which is different from showing something containing a barbiturate which can also be tested for. its really was y to do and costs pennies. you can get ones that test for specific drugs or multiple drugs aswell
and lastly if you are going o scam people why not just send water, why make the effort to put something different in the bottle? especially seen as N in mexico is so cheap to purchase. they can sell the stuff at such a massive mark up why would you put something else in the bottle so you can sell a few bottles before being found out, or sell thousands and make a shit load of money selling legit stuff. i suspect drug dealers who want continuous custom would do the latter.
I would also think by now it would have been reported in the PPH. it isn't just people on here that buy N, EXIT members buy it aswell and have it tested and report findings.