How to get the icon path of an audio device

I am writing an AHK script that uses audio devices. I'm using the Vista Audio library, and I have added some more functions to get additional data about the devices beyond their name. These functions are to get the device description and device icon:

GetDeviceDesc(device)
{
    static PKEY_Device_DeviceDesc
    if !VarSetCapacity(PKEY_Device_DeviceDesc)
        VarSetCapacity(PKEY_Device_DeviceDesc, 20)
        ,VA_GUID(PKEY_Device_DeviceDesc :="{A45C254E-DF1C-4EFD-8020-67D146A850E0}")
        ,NumPut(2, PKEY_Device_DeviceDesc, 16)
    VarSetCapacity(prop, 16)
    VA_IMMDevice_OpenPropertyStore(device, 0, store)
    ; store->GetValue(.., [out] prop)
    DllCall(NumGet(NumGet(store+0)+5*A_PtrSize), "ptr", store, "ptr", &PKEY_Device_DeviceDesc, "ptr", &prop)
    ObjRelease(store)
    VA_WStrOut(deviceDesc := NumGet(prop,8))
    return deviceDesc
}

GetDeviceIcon(device)
{
    static PKEY_DrvPkg_Icon
    if !VarSetCapacity(PKEY_DrvPkg_Icon)
        VarSetCapacity(PKEY_DrvPkg_Icon, 20)
        ,VA_GUID(PKEY_DrvPkg_Icon :="{CF73BB51-3ABF-44A2-85E0-9A3DC7A12132}")
        ,NumPut(4, PKEY_DrvPkg_Icon, 16)
    VarSetCapacity(prop, 16)
    VA_IMMDevice_OpenPropertyStore(device, 0, store)
    ; store->GetValue(.., [out] prop)
    DllCall(NumGet(NumGet(store+0)+5*A_PtrSize), "ptr", store, "ptr", &PKEY_DrvPkg_Icon, "ptr", &prop)
    ObjRelease(store)
    VA_WStrOut(deviceIcon := NumGet(prop,8))
    return deviceIcon
}

Both functions are slightly modified versions of the VA_GetDeviceName function from VA.ahk:

VA_GetDeviceName(device)
{
    static PKEY_Device_FriendlyName
    if !VarSetCapacity(PKEY_Device_FriendlyName)
        VarSetCapacity(PKEY_Device_FriendlyName, 20)
        ,VA_GUID(PKEY_Device_FriendlyName :="{A45C254E-DF1C-4EFD-8020-67D146A850E0}")
        ,NumPut(14, PKEY_Device_FriendlyName, 16)
    VarSetCapacity(prop, 16)
    VA_IMMDevice_OpenPropertyStore(device, 0, store)
    ; store->GetValue(.., [out] prop)
    DllCall(NumGet(NumGet(store+0)+5*A_PtrSize), "ptr", store, "ptr", &PKEY_Device_FriendlyName, "ptr", &prop)
    ObjRelease(store)
    VA_WStrOut(deviceName := NumGet(prop,8))
    return deviceName
}

The first of my functions, to get the device description works, but the other to get the icon path returns nothing. In addition to trying to get the DrvPkg_Icon, I have also attempted to get the DeviceClass_Icon and DeviceClass_IconPath with no success.

I have the PKEY reference here and the IProperty method number reference here.

I can't figure out what I'm doing wrong. Is it possible that the code is working correctly and that these values are empty (according to the WinAPI documentation, a device is only guaranteed to have a friendly name, a description, and an interface friendly description)? In which case is there another way for me to get the device icons?

I just don't get why it's not working. Thank you