British Airways have their own lost property co-ordinator and if you discover you've left something on board they'll contact the cleaners, the turnaround manager or send someone to check the aircraft if needed. If the crew find anything then it gets handed in at Arrivals Customer Service.

All items are then passed on to bagport the following day, the cleaning companies do the same. You can check if your item has been found on the followin website www.missingx.com

Bagport check a similar log when called to see if your lost item is with them.

Personally, I've left my wallet on board a BA aircraft on one occasion and my iPod on another, both times my items were found by calling the following day. When I left my iPod on a CX flight (as you can tell, I'm pretty forgetful) it was never seen again.