What discrepancies do Ravi and Pip see in the case against Sal?

Pip points out that it makes no sense for someone as smart as Sal to text Andie 112 times in order to create the appearance of innocence and then keep the most incriminating evidence of all--her phone--or fail to properly wash her blood from beneath his nails over a period of more than three days. Ravi adds that he does not see how Sal would have had time to hide Andie's body so well that it would still be missing after five years.