This is going to come off as a newb question, but a few months ago I saw a provider. Things were going well until I began to lose my erection with the condom we were using. The provider said “let me see if I have a girl one” stepped out of the room, and came back a minute or two later. I was intrigued because I had never had sex using a female condom.  

When the provider returned, she instructed me not to come inside her because “sometimes it moves around”. We proceeded to continue on and honestly, it felt damn good. I pulled out before I was about to cum and finished CIM. After the appointment, I was like “Damn, what have I been missing?”.

I started doing some research on the female condom, I read about the outer ring that remains the vagina. Now it’s been a few months already, but I don’t remember any “ring” being visible outside her vagina, around her labia.  

Did the provider insert a diaphragm or a female sponge, and I just assumed she used a female condom?

Ladies/providers, please chime in as well!

In my once or twice experience with the female condom, there was a section that hung outside the body.  You kind of lose the point of protection if it starts somewhere up inside.  But my experience is obviously limited.

It sticks out. If she was using one you would have seen it.

1.  She inserted the entire FC into her pussy, including the ring, which is supposed to remain outside.  I have no idea why she would do this, but is IS an incorrect way to use it and does carry some risks of your semen ending up outside the FC . . . . . .  OR

 
2.   She did you bare and didn't want you to know it so she wouldn't have to worry about it being in a review.  Its called plausible deniability.  

...an external portion of the FC showing outside her vagina.

I have two fave providers who use FCs almost exclusively (only time they use the male condom is a the client's request). Including duos, I've had 30+ sessions with them over the last few years.

I have ALWAYS seen a portion of the FC on the exterior. In fact, to engage in a bit of oral stimulation to her/their clits, I need to use a finger and gently set it to one side to lick enthusiastically.

I can't think of a reason why there WOULDN'T be a visible exterior part of the FC if it was installed properly.

Looking at the illustrations on the package of an FC, it shows it installed with a visible outer portion.

Buena suerte!

A female condom hangs out of her pussy like a little trash bag. She probably went to the other room to look for one, and realized she didn’t have one and said fuck it. She just did you BB and that’s why she didn’t want you to cum inside.

This.

 
There's no reason to tell you not to cum inside if she used a FC. Did anyone ever tell you not to cum inside while you were wearing a regular condom? Exactly.  

Unless shes the type of girl who puts a tampon string inside and then fishes it out for fun, she fucked you BB.

and as others have said you will definitely see the bottom of the female condom that covers the outside.
There is also a ring that is inside the FC that holds it in place I know some ladies who remove the inside ring.
Perhaps she didn't know how to insert it properly cause once a FC is inserted it doesn't move around like a male condom that can unroll and get stuck inside her.

about 30 times with a few providers. They always inserted it into themselves right in front of me. One even had a very sexy routine when she did it. A portion of it was always visible. They even made sure that my cock went inside of it and not around it. Plus they always lubed the hell out of my cock prior to insertion.

The point of the FC is to be able to cum inside of it. Since she told you not to do it, she most likely fucked you BB as others have indicated.

I agree.  She fucked you bare.  

…. as others have stated, YES, it should have been visible.

It's very likely she did not have one inserted.   She may have been using a form of contraceptive instead, but obviously that does not provide the STD/STI protection of a female condom.  

 
There are some people who use female condoms INCORRECTLY, with the outer ring tucked just inside either the vagina or anus (yes, some use them for anal sex too).

No, I've never done this, but I've heard & read the "how-to" from a few who do.    
It's not as safe because the female condoms can, and probably DO, move around a lot....  mostly likely getting pushed up inside,  all scrunched up, meaning it would then be BB anyway.