I do know that if they claim to be selling pints, then they are required to serve pints. That is, ``pint'' cannot be used simply as a synonym for ``glass of beer''.

My guess is that you asked for a pint and they asked for a ``Sam Adams''. As to what actually happened beyond that is unknown to me.

As far as it being common to serve imperial pints, it's not rare, but it largely depends on the bar. I'd say that a general rule of thumb is that they're much more likely to if they have a lot of beers on tap. If they serve most beers from the bottle and have two or three crappy beers on tap, then you're more likely to get a beer in whatever size glass they could get cheap from the distributor.