Yes, it was valid.
"I absolve you from your sins" is generally considered the necessary part of the form of absolution (in the Latin Church) to be validly absolved. Though the Council of Trent (and St Thomas Aquinas) seem to suggest that "I absolve you" is all that is actually necessary for correct form:
"The holy synod doth furthermore teach, that the form of the sacrament of penance, wherein its force principally consists, is placed in those words of the minister, I absolve thee, &c: to which words indeed certain prayers are, according to the custom of holy Church, laudably joined, which nevertheless by no means regard the essence of that form, neither are they necessary for the administration of the sacrament itself." - The Council of Trent, Session XIV, Ch 3
"Pastors should not neglect to explain the form of the Sacrament of Penance. A knowledge of it will excite the faithful to receive the grace of this Sacrament with the greatest possible devotion. Now the form is: I absolve thee, as may be inferred not only from the words, whatsoever you shall bind upon earth shall be bound also in heaven, but also from the teaching of Christ our Lord, handed down to us by the Apostles." Catechism of the Council of Trent, The Sacrament of Penance