It was probably just a new strain. It is highly unlikely your weed was laced. Think about it, if you were a dealer, why would you lace weed with coke (which is a LOT more expensive than weed) and then sell it for the same price as normal weed? So unless you paid a shitload more than you would expect, I wouldn't suspect it of being laced. Plus if it was coke, you would have felt some numbness in your mouth. Just "tripping for 20 minutes" means it was probably no more than high-grade cannabis.