I had a similar experience a couple of years ago. The rear rim on my Trek hybrid split. Was expecting to buy a new one when I went to the shop. But they said Trek had a lifetime warranty on the rims. I had bought the bike brand new a few years before.

When I came back to pick up the bike they told me Trek refused to back up the warranty. Forget why. However they backed it up and there was no charge for the new rim. I told them I could pay but they said no. Bothered me a little but I buy stuff and have them fix the bike so hopefully it works out for both of us.