That is what you are claiming, but that is NOT what Pius IX is plainly saying.
No, that's exactly what Pius IX is saying; he's merely reiterating what St. Thomas taught on the subject. Invincible ignorance can never be salvific, merely exculpatory.
Pius IX is speaking of ignorance positively, not as you suggest, negatively.
Such a "positive ignorance" is exceeding rare, if at all:
"All ceremonies are professions of faith, in which the interior worship of God consists. Now man can make profession of his inward faith, by deeds as well as by words: and in either profession, if he make a false declaration, he sins mortally." (Summa Theologica Ia IIae, q.103, a.4)
You can believe that Pope Pius IX was "correcting" Saint Thomas Aquinas, whom he praised elsewhere, but the text does not demand such a reading. In any case, let's assume that there are individuals who are in a state of "invincible ignorance" and in a "state of grace." Pope Pius IX also taught us:
To this witness is added the effective help of power from on high. For, the kind Lord stirs up those who go astray and helps them by his grace so that they may come to the knowledge of the truth; and also confirms by his grace those whom he has translated into his admirable light, so that they may persevere in this light, not abandoning them unless he is first abandoned.
And,
The Church clearly declares that the only hope of salvation for mankind is placed in the Christian faith, which teaches the truth, scatters the darkness of ignorance by the splendor of its light, and works through love. This hope of salvation is placed in the Catholic Church which, in preserving the true worship, is the solid home of this faith and the temple of God. Outside of the Church, nobody can hope for life or salvation unless he is excused through ignorance beyond his control. The Church teaches and proclaims that if sometimes we can use human wisdom to study the divine word, our wisdom should not for that reason proudly usurp to itself the right of master. (Singulari quadam, 7)
In conclusion, if there are any individuals who are in a state of grace while invincibly ignorant of the One True Church, the Holy Spirit is still drawing those individuals into the One True Church:
And here, beloved Sons and Venerable Brethren, it is necessary once more to mention and censure the serious error into which some Catholics have unfortunately fallen. For they are of the opinion that men who live in errors, estranged from the true faith and from Catholic unity, can attain eternal life. This is in direct opposition to Catholic teaching. We all know that those who are afflicted with invincible ignorance with regard to our holy religion, if they carefully keep the precepts of the natural law that have been written by God in the hearts of all men, if they are prepared to obey God, and if they lead a virtuous and dutiful life, can attain eternal life by the power of divine light and grace. For God, Who reads comprehensively in every detail the minds and souls, the thoughts and habits of all men, will not permit, in accordance with his infinite goodness and mercy, anyone who is not guilty of a voluntary fault to suffer eternal torments (suppliciis). However, also well-known is the Catholic dogma that no one can be saved outside the Catholic Church, and that those who obstinately oppose the authority and definitions of the Church, and who stubbornly remain separated from the unity of the Church and from the successor of Peter, the Roman Pontiff (to whom the Saviour has entrusted the care of His vineyard), cannot attain salvation. (Quanto conficiamur, 7-8)
It is, of course, this "divine light" which is drawing all men and women into the Catholic Church, so that they "may come to the knowledge of the truth." Since these "positively invincible ignorant" persons are known only to the One and Triune God, Pope Pius IX reminds us:
For, in truth, when released from these corporeal chains "we shall see God as He is" [1 John 3:2], we shall understand perfectly by how close and beautiful a bond divine mercy and justice are united; but, as long as we are on earth, weighed down by this mortal mass which blunts the soul, let us hold most firmly that, in accordance with Catholic teaching, there is "one God, one faith, one baptism" [Eph. 4:5]; it is unlawful to proceed further in inquiry.