Customs paper left in passport?

Hello.
When I was in Japan last winter, I bought a tablet in a duty free shop and got a custom paper attached to my passport. Thing is, when I was returning to my country I forgot to check in at the customs (the officer told me to go straight to the immigration) and the immigration officer said nothing, so I ended returning without lending the paper and just noticed later.

Now I'm worried that I will have problems when trying to get in Japan again. Do they stamp your passport when they get the customs paper? What they do with it? Will I have problems in future? Should I keep the paper or can I throw it away? Thank you.

Don't worry ;)

They don't stamp your passport or do anything when they remove the forms.
So you can take it out by yourself!

The imigration officer will notice nothing Records of tax refunds are only handwritten on forms (i.e. no electronic records) and I doubt very much they are able to match all the forms filled by retailers and the forms handed in at customs.

Or if you really are afraid make a new passport.
There will nothing on it ^^