Say I've attacked with Bomat Courier three times, and they're the only cards I have that are exiled face down. Therefore when I search my library, I am in principle able to deduce which cards are under Bomat Courier. This could matter a lot if, e.g., two of those cards are a Force of Will and a blue card to pitch to it (the Force of Will is even immune to targeted discard).
However, to figure out what's under Bomat Courier from searching my library is time-consuming. Therefore, can I just peek at the cards under Bomat Courier whenever I search my library?