Apple Wallet Has Reset

Ok so I have been using apple wallet for a long time. It has been set up with my debit card for Apple Pay which I use regularly. It has all of my frequent flyer cards on there for when I travel and a load of boarding passes. Yesterday I went to go on it to retrieve a boarding pass for my flight and it looked as though it had never been used before. None of my cards were on there, no boarding passes. I didn't do an update or change any settings, it appears to have just happened out of the blue. Has this happened to anyone else. Anyone know why it has happened? Not the end of the world because I can add my cards back on there but I kind of liked having all of my old boarding passes on there so I could easily see which dates I have flown on etc. Would like to know a cause so I can prevent it happening again.