12 Weeks and Counting & They’ve Lost It

Hi everyone, wondered if anybody had some experience/could help…

The timeline so far for my renewal is this:
Application submitted: 13th February
Posted passport: 18th February
Received Durham Passport Office (Signed for post): 21st February
About 5 phone calls including to the complaints line later, ‘Documents Received’: 28th March
Application processing: 28th March
…

And then nothing.

I’ve rang again and submitted a formal complaint two weeks back and haven’t received a call. This morning I’ve received an email saying that my passport was not linked to my application and I need to send an LS01 form as I need to declare it lost. It can only have been lost at the passport office as I sent it signed for and have the signature saying it has been received.

I’ve been waiting 12 weeks since they received my passport and to be honest, I’m less concerned about the delay than the fact they said they received my passport and 12 weeks later are telling me they’ve lost it.

Does anybody have any experience of the office losing their passport? Do you know if there is some compensation available or is there a more official complaints procedure rather than endlessly calling them and submitting forms?

Thanks in advance for any help!