Just wanted to share my story that was quickly resolved with a happy ending!
Left my bag in the overhead rack on the Southeastern Charing X to Hayes train (got on at London Bridge and off at Catford Bridge) on the 17:31 service last night (Monday). It had my MacBook Pro, chargers, sunglasses, clothes, PlayStation Portal, pulse explore headphones, toothbrush - a lot of expensive and important stuff!
Only realised when I got home and immediately filled the lost property form online. After a terrible evening worrying and horrible nights sleep, this morning I called Southeastern customer service as I figured the staff may have found it whilst doing a one-over on the train at the terminating station (Hayes). The operator called through to the station for me and my suspicions were correct - they had my bag at Hayes station! As it hadn’t been collected to go to the main lost property office at Canon Street they said I could go and grab it, and I’m just on the way home now with my bag and all the precious items are inside.
If you end up in the same position as me then I want to let you know that you may well be able to get your stuff back! The phone staff were actually very helpful in contacting the station for me and helping to circumvent what by all accounts can be a lengthy recovery process for lost property!