Don't use the italki search , use your regular internet browser. Every member has a specific URL for their profile page. Yours is https://www.italki.com/user/5835388 So if when you say you have his ID you mean the #, in your browser search box type https://www.italki.com/user/ your friend's user ID # If you only have his username, in your browser type : username italki

tutor

yep , try to use one browser in a PC or in your phone

Go to community, then language partners, enter all the information you know about him like country of residence, languages etc, and then browse, and hopefully you can find them that way.

Try to contact italki, they might help you.