As you stated the play, it sounds like the BJ BELIEVED, rather than "thought", he saw the ball touch the ground (which prompted him to "SELL" the call by patting the ground). "Seeing" something should always trump not-seeing, or not being sure about seeing something and the LJ was correct in not challenging a specifically affirmed decision, due to his own acknowledged UN-certainty.
When there is mutual doubt about a call, or considerable CERTAINTY about challenging a call, it's appropriate to immediately confer with the other official (as privately as possible) discuss and resolve and differences and agree on the call to be made. Having "seen" something SHOULD ALWAYS TRUMP suspecting something.
"Getting the play right" is of primary importance, but so is having confidence in your crew mate, to the extent of supporting his firm decisions.
"SELLING" a call can be extremely useful and helpful in specific situations, and should be used judiciously and sparingly only when the situation, and circumstance, dictates. Like Garlic, when applied in the right amount (circumstance) can be very beneficial, when over used, can be disastrous.