I am unable to reach one of my faculty member through email, phone call or even in person, who have agreed on providing me with a recommendation letter. He is not replying to my email, phone number is unavailable and even not coming to the office. I do not know what is wrong or what is the matter, I might miss a deadline of a university which I am really intending to attend.I have given him multiple reminder and not even sure whether he has seen them or not.
Here are some ideas (from high to low priority / potential efficacy ):
Explain administrative stuff of the faculty your situation and ask for help. Maybe they know that he/she is abroad and will come soon. Or he/she is sick and will likely not be able to help you.
Find his/her students and explain your situation and ask for help.
Talk to some other faculty member asking whether he/she can help you to locate him.