Exactly the same fate befell me today, albeit for BA1394 LHR-MAN.

Tried to OCLI last night when I rolled in, and it said that it "couldn't validate my booking."

At T1 the SSCI asked me for my credit card, then said further ID was needed, (ie BAEC card) and then asked me for my credit card again.

Then told me to check in at a desk.

Was cutting in pretty fine at this point, so smiled nicely at the lady at FBD. Who gave me 8C. Which was much better than I feared. And middle seat empty, too.

Never happened before. H ticket, bought with a BA Amex on ba.com. I had changed the booking, mind. Maybe that ballsed it up.