Yep, wanted to know what the procedure is. I did this in several airports (MUC comes to mind) but only after confirming with others that the airport actually has a well defined procedure for late bag pickup (i.e. bag goes into baggage office, does not just walk away). As an example, asked same question about MUC and got an unequivocal "your bag will be picked up and held at the office" from several people, so I felt pretty confident about it.

Can't go to the lounge later as I am actually not taking the same connection that is on this ticket, but rather transfering to the other airport on a different flight - long story. I.e. I will have a boarding pass for TK flight out of IST but I am not actually going to fly it.