Missionary in MoV CS purchase

So I was using Venice in a map and I ended up buying a city state. One of the units in the CS was a missionary, but the missionary didn't have a religion. I attempted to spread the religion to one of my cities but there was no spread religion button. Same goes for disbanding the missionary where the missionary didn't give any gold in return for its disbanding. The only way I was able to use the missionary is by exploring the map with its 4 movement. Has this happened to anyone?

Missionaries don't usually give any Gold on disbanding. However, that's still weird that it didn't keep the religion of whoever originally bought the damn thing.