They will request a copy of his entire file from the FAA. If he ever got a pink slip on a checkride, it will be in there. As long as no pink slip involved then they won't find out. If he wants to see what the FAA has, all you have to do is write Oklahoma City and they will send the entire file. Takes a couple of weeks and costs like .05 a page.

Always a good idea to do this before any interview so you can see exactly what is in there. I know a guy who interviewed with a regional and got the job, only to find out in training a DE had sent an erroneous pink slip in on him. It came up in the PRIA check, and fortunately he was able to prove otherwise with his logbook so they let him stay in class.