What was your "oh, they wanted more than coffee!" moment?

In an episode of the TV show Seinfeld, a woman invites George Costanza for a cup of coffee in her apartment after a date. George rejects the offer, saying if he drank coffee that late he would stay up all night. The woman leaves the car visibly underwhelmed. After a second, George realizes "coffee" meant "sex" and he just lost a great opportunity.

Have you ever had a moment like that (not necessarily about romance), in which a silly misunderstanding led to the loss of an opportunity?