Some users have reported that after editing the cost basis for a token to be zero, the transaction will disappear from view in the Transactions page.

This is because the transaction is now considered a dust transaction and users who have enabled will not see this transaction shown.

To re-enable the view of dust transactions, users can toggle off this filter setting within their Transactions page (screenshot attached).

You can upvote this forum post to indicate you are experiencing this behavior. The post status will be changed to once a fix is rolled out to all users. Up-voters will be notified of the status change.