Originally Posted by LondonAndy

So you picked up someone else's bag and you want BA to play courier for you - exactly what have they done wrong?

I was that Madrid passenger in Seattle once - it was clear when there was only an identical suitcase to mine (less all the stickers, the tags, the luggage label ) left on the luggage reclaim belt that someone else had picked up my case. BA were happy for me to take the other case, and swap it at the city centre hotel virtually before the passenger had realised that they had the wrong case - "they all look the same" apparently

You've made an error, if I were you I'd go to Heathrow - if I was the Madrid passenger I would want to know why you had kept my bag for so long.

A Wikipedia definition for you - Theft is the taking of another person's property without that person's permission or consent with the intent to deprive the rightful owner of it. Maybe the original intent wasn't to deprive the rightful owner of the bag, but it is now.