was the baptism itself valid?
The real question is, valid for what?
Let's look at it objectively first of all. Christ commanded his disciples to "Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit". Matthew 28:19
I have to ask, if these people claim to be disciples of Our Lord Jesus Christ, why then do they not do as He said and baptise in the Name of the Holy Trinity? Most probably, because they confuse the meaning of "Baptism in the Name of the Lord Jesus" referred to in Acts.
In the book of Acts, the term "Baptism in the Name of the Lord Jesus" is used to differentiate between the Baptism of St. John the Baptist and Christian Baptism, as the book of Acts itself attests when we are told that St. Paul:"found certain disciples, and said to them: received ye the Holy Spirit since ye have believed? They said to him: but furthermore whether it be of the Holy Spirit, we shall hear. He said to them: into what were ye baptised? They answered: into the baptism of John. Paul then said: John indeed baptised with the baptism of repentance having proclaimed to the people, that they should believe in the One coming after him, namely, Christ Jesus. Having heard this, they were baptised in the Name of the Lord Jesus: and Paul laying his hands on them, the Holy Spirit came upon them" (Acts 19:1-6).
The things to note from this are:
1) Acts calls them "disciples" even though their baptism was not valid- the Orthodox Church would call them "catechumens"- ie. disciples in the process of being taught in preparation for baptism.
2) They had been baptised "into the baptism of John"- which is, they had been immersed in water (baptised) to show repentance
of sin- but this baptism does not grant remission
3) Even though they had received this baptism of John, they must be "Baptised in the Name of the Lord Jesus" (i.e. recieve the Baptism of the Church- the Body of Christ). Their previous baptism was not "valid" for initiation into the Church.
4) To distinguish between the two baptisms, one is called "the baptism of John" and the other is called "Baptism in the Name of the Lord Jesus"- meaning, the Baptism which Christ instituted as opposed to the one John instituted. And which baptism did Christ institute? "Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit". Matthew 28:19
5) the "Didache"- an ancient Christian text dating to Apostolic times, and which most scholars agree predates the last of the Epistles and the first of the Gospels clearly describes the baptisimal practice of the first Christians as being triple immersion in the Name of the Holy Trinity.
So, in terms of Christian baptism- what you received doesn't resemble it in any way other than the use of water.
Secondly, baptism is (among other things) the granting of the remission of sin and initiation into the Church and for the reception of the Holy Spirit (Chrisimation- i.e. the "Laying on of hands" spoken of in Acts). As far as the Orthodox Church is concerned, there is, and can only ever be "One, Holy Catholic and Apostolic Church"- therefore, any baptism performed outside the Church, (ie by someone who is not themself a member of the Church) is invalid for reception into the Church, even if this baptism was done by triple immersion in the Name of the Holy Trinity. The Church can, in some cases, render this baptim valid retrospectively
by Chrisimating the person, but as it stands, without Chrisimation or some other form of validation by the Church, any baptism outside the Church is invalid for reception into the Orthodox Church.
Hope this helps.