I have abandoned my case once. We got diverted into STN on a VS from JFK during a Heathrow snow meltdown. Total chaos, multiple widebody diverts followed by Stansted itself closing so all departing flights also needing luggage return. I asked a handling agent and she said I'd be fined if I left without it and it was illegal due to customs issue!

With time getting on and a trip back to Bucks ahead I decided to head home. Reported it lost to Virgin and it had already made it into the standard lost luggage system. They suggested it would need to come to Heathrow and then be shipped out to me so would take a couple of days. Lo and behold an hour later the case turns up in a taxi to my office in London.