Dollars to donuts the anonymous poster is Stubborn. He's been on record before essentially removing intent from sacramental validity because it is impossible to know.
Nope, the posts I made here I clicked the box. Except for #4 where I forgot - I said: Chlorinated water is "real and natural". Consider that Baptismal water always contains salt and holy oil.
Second, all the sacraments, once administered, are presumed valid by the Church until proven otherwise.
If it were any other way, what would the Church preserve and defend? The answer of course is, nothing.
The OP is worrying about absolutely nothing, the child is certainly baptized - according to what the OP described.