Tap cross-contamination

I think the waiter served raspeberry beer in your glass by mistake and when he (she) found out immediatle shift to your requested beer leaving some of the other beer in there. It happens a lot when bar has lots of taps and they don´t identify them because of constant keg rotation.

Edit: Oh I see that someone wrote this first.

 

I highly doubt that the kegs were switched at any time. I am almost 100% sure that Lindeman's has a different keg coupler than Sierra Nevada kegs

 

I've had that happen twice in the past year at two different places. At one had a Spaten Oktoberfest that was distinctly fruity. The bartender was raving about it when I ordered. When I called him back over and explained to him that it was clearly off, he poured himself a sample in a shot glass and smelled then tasted it. "You know, we did just have Leinie's Raspberry Shandy on this line..." Ding ding.

Second time was at a BWW where a Madtree IPA was also way off. Another shandy on the tap right before it.

In both cases they were happy to replace my pint with something else.