Original passport not returned

Hello

I applied for asylum in 2011 and travel document after getting leave to remain as refugee. My original passport (which I used to enter this country) wasn’t returned. I was a minor and didn’t know what to do.. now that I have applied for British passport after my neutralisation, HM passport centre want my original passport that I used to enter uk. I don’t have it, I email home office but no reply, please tell me what can I do? I sent a cover letter explaining the passport issue to him passport office but it’s not enough.. any help would be much much appreciated