PSObject Array of Arrays Return Powershell Read Individual Items/Rows

I am using one Function to call another and returning a PSObject array or multiple arrays (I think). The return after each looped object is a set of values. The data in $a in Function Test2 is below but it's count is 3, meaning three objects or arrays, one for each folder. This seems pretty normal and if I wrote it to a CSV for a report I would be fine, but I am looking to manipulate the data in each array. When I try to manipulate the data it's trying to manipulate the arrays and I can't search or use items in each row. I also don't know how many folders I have so the solution needs to be universal and expandable. I don't know how to gain access to each row in all the arrays easily.

Function Test1 {
 [cmdletbinding()]
param(
    [Parameter(Position = 0, Mandatory = $true)]
    [string]$Folder
)

$array1 = @("Folder1_Test1","Folder1_Test2","Folder1_Test3","Folder1_Test4","Folder1_Test5    ","Folder2_Test6","Folder2_Test7","Folder2_Test8","Folder2_Test9","Folder3_Test1    0")
$array2 = @("Folder1_Test1","Folder1_Test4","Folder1_Test5","Folder2_Test9")


$data = @()
Foreach ($item in $array1) {
    If ($item -match $Folder -and $array2 -notcontains $item) {
        $Obj = New-Object PSObject -Property @{
            Folder = $Folder;
            SubFolder = $item;
            Message = "$item not found.";
        }
        $data += $Obj
}
}
Return ,$data
}

Function Test2 {
$Folders = @("Folder1", "Folder2", "Folder3")
$a = $Folders | ForEach-Object {Test1 $_}
$a.Count

foreach ($item in $a)
        { 
          $item.Folder
          $item.SubFolder
          $item.Message
        }
}

The output of $a is however the count is 3.

SubFolder      Message                   Folder 
---------      -------                   ------ 
Folder1_Test2  Folder1_Test2 not found.  Folder1
Folder1_Test3  Folder1_Test3 not found.  Folder1
Folder2_Test6  Folder2_Test6 not found.  Folder2
Folder2_Test7  Folder2_Test7 not found.  Folder2
Folder2_Test8  Folder2_Test8 not found.  Folder2
Folder3_Test10 Folder3_Test10 not found. Folder3

How can I get access to each row inside each object? I want to be able to search through a subfolder and then identify the folder it's on and write the message, something like this:

$a | ForEach-Object | Write-Host {"Subfolder $($_.Subfolder) is in $($_.Folder) and error message is $($_.Message)"}

Thanks in advance.