If you can't find the stickers that you purchased, go to the More tab > Settings > Purchase History and click the 'Restore Purchase' button at the bottom of the page.
If your account has a record of your previously purchased stickers, your purchase history will automatically update.
If the sticker you were looking for has been added to the list, download it and start using it in your Between chats.
1. Please be aware that your purchase history also gets deleted when you delete your Between account.
2. Please double check whether you are using the ID you used to purchase the stickers.