You cannot directly see someone’s hidden Last Seen on WhatsApp
If their Last Seen is hidden, WhatsApp does not provide a way to reveal it
You can check whether they are currently online if their online status is visible
You can look for read receipts if they are enabled
You can infer activity from message delivery and reply timing
You can ask the person to share their Last Seen settings with you
You can check mutual group activity to see if they are active on WhatsApp
You can use WhatsApp Web or another device only for your own account, not to bypass privacy settings
Do not use third-party apps or hacks claiming to reveal hidden Last Seen
Respect the person’s privacy settings