Good title. I don't make drug mistakes, but you can't always rely on what a powder is can you?
Thinking it was methylone (it should have just been methylone) I stuck 250mg up my arse (gf did too) only to have the darkest hour of my life (gf too) because it turned out to be a mix of methylone and ketamine. And you should NEVER stick ketamine up your arse. I found out why the hard way. Saved by mephedrone by the way. Brilliant drug.
Also a mate bought 'cocaine' in a pub in Brixton. I could even fucking see it was obviously a crushed up pill of some sort, it wasn't even fully crushed properly. Turned out to be physeptone. Not enough there to cause fatality, or even any effect, but it was the worst sting (for about an hour) of anything I've ever stuck up my nose.
Best mate (I wasn't there) weighed out MXE, but he's shit at maths, and he thought 50mg was the same as 0.5 on his scale. Him and a mate, massive disaster, deep head fuck for hours and smashed furniture etc.