This question is worth re-examining and it supports the theory of St. Augustine, of Fr. Feeney and others; namely, that the grace of justification, the first necessary grace for salvation, is often bestowed on the soul before Baptism through Baptism of Desire. But the grace of final perseverance, the last and sufficient grace that completes salvation, is bestowed on the person after the Sacrament of Baptism. It seems to be a striking confirmation of that theory that we have some ancient sources in Tradition that say those waiting in Limbo were apparents the recipients of the sacrament of baptism in some extraordinary way, after which they went straight to Heaven.