After I graduated (B.S.), I did not get job and what I did was contacted international student coordinator saying that "it had been 80 days of my OPT and I have not found the job but I am volunteering in one of the professor's lab". To be honest, I was not volunteering and the name of the professor that I gave them was my academic advisor during my undergrad. Then I got an email next day from the coordinator saying that he had reported my situation to the DHS (or something office) and I had OPT till one year. That's how things got solved. Time is tough these days to find job so I believe it won't be so hard to get extension after 90 days. Also I have not heard of anyone saying to have a problem beyond 90 days. Goodluck