The first step is to scan your colored ID card and then send it to the KRA social media page, preferably their Facebook Page or Twitter handle, through direct message and tell them you have forgotten your KRA pin. Then request them to send it to you. They will respond within an hour and you will be able to retrieve your lost KRA pin. Using social media to seek assistance is the fastest way to get a response.
You can email KRA at email@example.com and send them a colored scan of your national identification card on both sides. Preferably use the email address you used to sign up on iTax. However, this method is slower as compared to reaching out to KRA via their social media handles.