Data failed to be returned from firebase [swift] - swift

Question

Firebase not returning data for a given record, despite it being present in the db .
I have some data in firebase that looks like this (2 records to be exact), and conforms to this structure
{
users : [
SOmeBig0lDID:{
credentials:{
name:"bob"
number:"[phone]"
}
}
..... other users
]
}
In my app i am iterating over the phone numbers in my contact list and issuing a search for each number to identify which is a user. When i issue the search, i get back a value for one of my records, but not the other.
In terms of implementation, as you can see below, I am waiting for a search to complete before issuing another one , here is my code. Im wondering if it is just a corrupted record, in which case this is also very worrying.
I am also 100% sure that the phone number formatting is correct when the query is submitted to match that stored in firebase.
//get a list of correctly formatted phone numbers up here
func getuser(number:String,count:Int,total:Int){
print("Looking for :" + number+"|")
let usersRef = Database.database().reference().child("users")
let query = usersRef.queryOrdered(byChild: "credentials/number").queryEqual(toValue: number)
query.observeSingleEvent(of: .value, with: { snapshot in
for child in snapshot.children {
let snap = child as! DataSnapshot
var dict = snap.value as! [String: Any]
let creds = dict["credentials"]!
print(creds)
}
if count < total-1 {
getuser(number:finalNumbers[count+1], count:count+1, total:finalNumbers.count)
}
})
}
getuser(number:finalNumbers[0], count:0, total:finalNumbers.count)
I am expecting to get back the record for a number that i am querying , but i do not. I have verified that the number i am searching for is the number that is in the realtime database and have gone so far as to change the number in the realtime db to match exactly what i see the client issuing (it was doing this already however for completeness i wanted to ruled out the client doing some odd encoding) and yet still the record is not returned.
Oddly if i set the number of the record i am not getting returned, to the number of the record i am getting returned , i get both back. (both number fields have the same value).
If this is an issue with firebase more generally that others have experienced , please comment, i don't want to be using somethign that just doesn't work consistently.
any thoughts let me know, been stuck on this issue for a while.