Foreign Birth application lost?

At the end of December I submitted an FBR application to the Irish Embassy in London. Due to it containing old douments (birth certificates) that my mum didn't want to risk losing, I posted it through the postbox of the embassy (they were closed and i couldn't make it in when they were open).

I contacted the embassy to see if they have received my application as I didnt get confirmation, and they just today said they haven't yet. Have I messed up by not handing it to someone or posting it recorded, or could it just be sitting in a pile in the embassy waiting to be opened? I know that there is a huge waiting time at the moment for applications to be processed but I thought i would have at least received confirmation by now. I'm worried that the application is lost and I have lost precious documents.