I was flying AA earlier this year, and had a nice Exit Row seat. Guy who sat next to me had this happen to him (I was aisle, he was window, no one in middle). Super friendly guy who had some pass that allowed him to fly first class on AA for the rest of his life for free (or so he claimed). Based on the way that the FA treated him, I didn't doubt it - he insisted that they give me the royal treatment as well (and they complied). At first, we couldn't really figure out why he got bumped, FA wouldn't tell us. Eventually we asked if it was an air marshall, she said "I recally can't say" with a big grin on her face.
Good for you for laughing it off, life's too short to be pissed about getting "downgraded" on a SYR-DCA flight. Now an LAX - PHL redeye, maybe . . .