I would think that when most people want to know more about TM, they googe until they run across the TM Association site. They have a forum there: http://www.myelitis.org/forum/
A certain percentage of people with MS are never told that what they experienced was TM, especially if they are dx fairly quickly. In my case, I had my first TM attack in 1991, and they basically said "you may have gotten a virus in your central nervous system (spinal cord) ... but we are leaning towards this being MS (in the longer run)". I had had other weird symptoms previously, probably a MS attack actually, which was the reason they were leaning towards MS at the time ...
I wasn't told about "TM" per se', and I'm not even sure they had invented that name for it at in those days. When I had my second TM attack, in 2003, they had a name for it by then; Transverse Myelitis due to MS. Effectively it just became "MS" at that point though.
It's kinda like when someone gets Optic Neuritis, that might be all they are told at that point. ON can happen for many various reasons, so unless they have reason to believe it is DUE to MS, they often don't say that. (It is prudent if they do a MRI at that point, but many times they don't too).
So nowadays a person might only be told TM, if they only have spinal cord lesion(s), and then they wait to see if it develops into MS. The stats are so varying in that degree, and I've read everything from 15% to 85% of TM cases eventually end up as MS or NMO.
People with TM have many various diseases though, and depending on the cause, the results will be different. For instance, someone with MS/TM will likely develop brain lesions eventually and have different kinds of attacks in the future; someone with NMO/TM have a more serious longer-term outcome; but someone with idiopathic TM is going to be in a different (one time) situation. Also, the damage we are left with is varying, no matter what caused it.
So it is often even difficult to compare notes on what we are likely to experience, especially over the longer run.