i left my backpack in keisei train skyaccess

so i came from indonesia to japan for holiday. but on my way to narita airport using keisei takasago skyaccess i left my backpack accidentally in the train (on 20 January), and i realized it when the train already head off to haneda (if im not mistaken) and now i already in Indonesia again. is there any way that i can get back my backpack again?

Did you report the loss at the station after you got off? At the destination the staff tends to check the train and keep the found items at their lost & found office for a week or so, after which they turn them into police.

Sorry to hear you lost your bag.

There is no direct connection between Narita and Haneda airport by Skyline.

You can contact the Keisei lost property office can only be contacted by phone between noon and 7pm weekdays.

The phone number is: 03-3621-2315

Website: https://www.keisei.co.jp/keisei/kouhou/lost.htm

You need to describe your bag in detail including the contents.

If you can understand Japanese or using translator, you can check the police's keeping your item.
https://www.keishicho.metro.tokyo.jp/sodan/otoshimono/index.html

thankyou so much for the answer.
on the day i left it, i already ask around, but i cannot speak Japan, so all i say is "i left my backpack in train" and they refer me a number, which is i cannot call it either because i also have to check in for my flight.
but thank you so much for the answer, i'll ask around for translation.
thank you