Debian installer unable to detect preseed.cfg file

I am trying to do a fully headless Debian install for an old x86_64 Windows NAS that has no display output. Aside from serial interfacing (which is not documented for my hardware), preseeding is my only option. As per the official documentation, I created a modified install image with the preseed.cfg file (shown below, configured to do most of the installation over *network-console*) inside the initrd.gz archive.

d-i debian-installer/language string en
d-i debian-installer/country string AE
d-i debian-installer/locale string en_US.UTF-8

d-i keyboard-configuration/xkb-keymap select us

d-i netcfg/choose_interface select auto
d-i netcfg/get_hostname string HP_StorageWorks_X510
d-i netcfg/wireless_wep string

d-i hw-detect/load_firmware boolean true

d-i anna/choose_modules string network-console

d-i network-console/password password r00tme
d-i network-console/password-again password r00tme

However, when I test the modified install image in a virtual machine and enter the installer with the modified initial ram disk image, it does not recognize the preseed file. I just the see the option to select the language as if the pressed is not there. What could be the issue here? I extracted the modified install image and made sure the preseeding was done correctly. Better yet, is there an easy way to specify the preseed file without having to modify the installer image myself at all?