Thank you very much for your response,
@SusieQQQ! I vaguely remember that at the airport, the officer asked me to look in the camera and did take my fingerprints, so I'm not sure how they could've missed it. Regarding contacting the representative, wow, thanks for the tip, I haven't even considered that since I thought that Green Card holders don't have a right to vote, so technically we're not their constituents. But I'll definitely try that!
But yeah, the situation is very frustrating. I didn't know such delays were possible, so I made plans to travel out of the US in September to take care of my medical-related issues, but now it looks like I'm indefinitely stuck here without any idea how much longer it's gonna take.