Actually on my first plat flight (which was to Delhi) I was opped.
As the queue was quite long I didn't bother to queue up until they cleared the masses.
When I went to the counter about to present my BC one GA said to the other one, don't worry if the system is beeping at a customer, if it is this one, here is his new BP.
I looked at the BP she put down and hey, there was my name. Got a nice flight in 5C (and some surprised looks of collegues that boarded after me).

The other time I was semi-opped was 5 years ago when travelling from EIN via CDG to LAX.
That day EIN - CDG was delayed due to bad weather and they rerouted me and my family to rows 1 and 2. Actually this was a 747 in the holiday season. They moved all C passengers to the upper deck and used the front for economy, which meant C seats and Y service (meals etc). My kids just loved it...