First off, what is the fiber?
Depending on that, I have found through the years, IF I get to be the first one to work on it, I have a fair chance to either remove it or make it look a lot better. I have also found that if someone has messed with it first, it usually does not come out.
Here is what I have found works some of the time. (Again, fiber content can make a lot of difference in the results). Using nylon as an example, that can be one of the fibers that can be hard to remove it from.
Mix Boost All with a Protein Spotter in a cup until you get a paste. Then apply the paste. It should be workable but not runny, remember, a paste.
Allow it to dwell on the stain for a reasonable period of time, it can be 10-20 minutes. Use of a white absorbent towel to gently agitate it NOT SCRUB. All you are trying to do is see if you get a transfer onto the towel. (you should have already done a dry crock test to see if it will move or not but I am sure you already know this).
If it moves, continue and vacuum it out. Repeat and the next time, put a towel over the paste and use a vapor steamer to heat the paste through the towel and see if you can draw it up into the towel. As long as you make progress, you can continue. You can also accelerate the paste by wetting it out a 'little' with more protein spotter (or ammonia as well).
I have had reasonable success with it, if I got to be first.
The paste is very aggressive and you can accelerate it to make it more so. The vapor allows it to accelerate it even more.
If you need to see an example of this process, let me know privately and I will share a video with you, if you would like to see it.
Hope the best for you. Of course, you can always cut it out and do a B.I.