We've all been fucked by a dealer once or twice. Nothing to do but let it roll off your shoulders and fire up what you did get. All part of the game.

I'd suggest buying a digital pocket scale. They're pretty cheap at anywhere from $15 to $40 USD and they're nice to have, just to make sure you're not getting ripped off or when your buddy stops by looking for a small bag. Just remember to account for the bags weight and to use caution when travelling with pot and a scale, in the U.S. that's a sure-fire way to get a "possession with the intent to distribute" charge.

Happy tokin'