How do we know that the Buddha was really enlightened, either? We can't see him now, or hear his words directly, other than through suttas recorded millenia ago and handed down by monks, whose integrity and/or accuracy of memory we must rely upon if we are to assume that they are basically unaltered...?
We don't really know, unless we have seen (the truth he speaks of) for ourselves. Believe me, if I see for myself (within) the self-less nature of the five khandhas, I will throw myself to the ground before the Blessed One's feet in gratitude, a thousand times (metaphorically speaking), knowing that he was right all along, and that it was only because he so carefully established his Dispensation here (on Earth) that I had the good fortune to do so; and I will finally feel totally comfortable with calling myself a Buddhist. But if or until that happens, I can't say with certainty that the Buddha is indeed 'rightly self-awakened, blessed and holy'. I follow the Path he (is said to have) laid out for us, because in all my searching over my 42 years, I just can't find a better teacher. I've tried; but no-one else knows as much about the human condition and the ways of the heart-and-mind, as the Buddha does (as recorded in the suttas).
Maybe only the enlightened can truly recognize the enlightened, and the rest of us kind of just muddle along and do our best...?
Then the Blessed One, picking up a tiny bit of dust with the tip of his fingernail, said to the monk, "There isn't even this much form...feeling...
perception...fabrications...consciousness that is constant, lasting, eternal, not subject to change, that will stay just as it is as long as eternity."