Of course, if such a person were to present himself for Holy Communion, he would have to be denied - baptism by desire does not convey a sacramental seal, and if such a person were to realize the truth of the Catholic Faith he would have an obligation to receive baptism.
I ran out of room on the last post and wanted to address your point about the
need for the person to receive the Sacrament of Baptism so as to recieve any of the other sacraments. Which is true.
But If one cannot receive any of the other Sacraments one is
not one of the faithful:
Catechism of the Council of Trent, The Members of the Church Militant:
“The Church militant is composed of two classes of persons, the good and the bad, both professing the
same faith and partaking of the same sacraments…”
cin.org/users/james/ebooks/master/trent/tcreed09.htm
St. Francis De Sales, says the same:
“The Church is a holy university or general company of men united and collected together in the** profession of one same Christian faith; in the participation of the same sacraments…”**[The Catholic Controversy, p. 161]
And that Trent states that there is nothing wanting in the justified:
Pope Julius III, Council of Trent, session 6, chapter 16
“For, whereas Jesus Christ Himself continually infuses his virtue into the said justified,-as the
head into the members, and the
vine into the branches,-and this virtue always precedes and accompanies and follows their good works, which without it could not in any wise be pleasing and meritorious before God,-
we must believe that nothing further is wanting to the justified…”
If nothing is wanting to the justified then how is it that they need to be Baptized to receive the other sacraments?
The answer is that Trent is speaking of those who have recieved Baptism and there are no other justified persons since Pentecost–only those who are Sacramentaly Baptized are:
members of the Faithful
justified,
eligible to participate in the sacraments.
Earlier in the same Session, 6, chapter 8, it says:
“because faith is the beginning of human salvation, the foundation, and the root of all Justification; without which it is impossible to please God, and to come unto the fellowship of His sons: **but we are therefore said to be justified freely, because that none of those things which precede justification-whether faith or works-merit the grace itself of justification.” **
Many will quote this as "proof’ of “Baptism” of Desire because it say ‘the root of salvation is faith’ but it is really saying the opposite of what “Baptism” of Desire advocates are saying, that the Faith of, for example, the catechumen, justifies, but it can’t be their faith as Trent points out (above) because nothing preceding justification suffices. So we are back to the Sacrament of Baptism only, that creates no conflicts with de fide teaching, also we receive Divine vitues of Faith Hope and Love from the Sacrament not before.
Finally even in mass we pray for "“those who have gone before us marked with the sign of faith.”
That mark is Baptism called the Seal of Salvation by the Fathers:
St. Cyril of Jerusalem, Catechetical Lecture 1,#3, 386AD:
“He gives not holy things to the dogs (Matthew 7:6); but where He discerns the good conscience, there
He gives the Seal of salvation, that wondrous Seal, which devils tremble at, and Angels recognise”
newadvent.org/fathers/310101.htm