iPhone lost by Apple Store

My iPhone was broken so I went to an Apple Store to fix it on warranty. They couldn’t do it and send it to a depot to fix it there. It was 1.5 month ago. The depot send the iPhone back to the Apple Store. It’s now 2 weeks and nobody knows where it is. I’m in the UK. Did anybody was in a similar situation? What could I do to get my device? Could I get a new one?