Nobody knows what that thorn is the flesh was, but it certainly does not negate the Word of God which declares that we are healed by Jesus bloody, broken body as demonstrated by all that were healed by Jesus in the Gospels, in Acts through believers, and today.
Take the issue of ETs, extra-terrestrials: naybobs tell us there is no such thing visiting the Earth. If just ONE is found doing so, the entire premise of none is negated. You want us to believe ALL faithful requests are granted yet the problem of Paul being denied healing because God said His Grace was sufficient negates you premise. Recall that Paul identified the thorn ‘in his flesh’.