I think the Exodus in-app exchange is ShapeShift, so probably they were the ones that froze your assets for some reason. According to
this support article, they are also working with FTX. Having your assets blocked is unfortunately one of the dangers of using centralized exchange platforms.
I doubt it's FTX. It's probably the in-app exchange, but they'll have to tell him which one he used (assuming that it's not already visible in the details of the transaction) because Exodus uses multiple providers and not just a single one.