I remember a long time ago I got some schwag ("poor" quality) and my friend called it 'Chaser weed' and after I smoked it, I knew why. I was pissed for about 20 minutes because I didn't get high.... thten I got stoned - and I got really stoned for about an hour, it backed off, and then hit me again .. it lasted a good 6 hours, and my two friends who smoked it had very similar experiences (even the one who I just gave him a bowl and he went off on his own) ... Could this have been one of these sorts of altered plants?