Buying missionary for minority religion

I have founded a religion, but my faith generation is pretty low and I am neighbours with the Celts who have very high faith generation. As a result, all my cities, including my capital which founded my religion, have been converted to the Celt religion.

When I earn enough faith to buy a missionary/prophet, will this missionary/prophet now take the religion of the city (i.e. the Celt religion) or will it take the religion I founded?

The prophets are always of your religion that you founded, but missionaries and inquisitors are of the dominant religion in whichever city you buy them in. So you can use your prophet to restore your original religion, but beware of missionaries or inquisitors, since those will be following the Celtic religion if you buy them, at least until your religion comes back.

The missionary will be whatever the religion is of the city it comes from.

A great prophet generated from faith accumulation will always be your faith. I can't remember for sure but I believe I read somewhere on the forums that a great prophet will ALWAYS be your religion if you create it since they won't be available had you not founded one.

I found that once my holy city had gone completely to another faith, thanks to my improper use of an inquisitor, even the indication that it was my holy city disappeared from the city title, but I was still able to get it back to my faith with a GPr.

Great Prophets are powerful - they combine what the inquisitor does with what the missionary does. So if you get a GPr over to a CS that has no followers of your faith, but several of others, the GPr can leave that CS with only followers of your religion, though it may take more than one application of his "preaching" to give the CS enough followers (more than 50% of the population) for your religion to be established there.

I discovered the other day that I could buy buildings and units with my faith points because another civ had converted some of my cities to their religion. This was just awesome!! Imagine having your religion without these choices (instead choosing tithe, guru, and the like) but still having the option to purchase religious buildings and units despite this. I would delay Industrialization a little to have a city that had most if not all these buildings, if only to see how it stacked up.

Just wish I would be able to see what the civs chose for their religion... I'm seriously thinking about going to war with a civ just to take their prophet if they come around... or maybe seek them out. When enough faith points come around then I would just convert select cities so I could get the building(s) then convert to another religion, and so on... Really cool!!

You can easily see what they choose, just go to the religion menu and click on the beliefs.