sorry, that is not true. the yellow card system is also for reporting adverse drug reactions (of which this is one)
The information i have given you is correct, and taken from the British National Formulary, which is the standard text that both Dr's and pharmacists use
i have here in front of me a "yellow card"
on it it says "the mrha welcoms yellow card reports on any suspected side effect", Which this is. Your doctor suspects your hair loss is a side effect of this medication, and has reported it as such. The more information they get, the better. It's very unusual for doctors to tell people about every single side effect, especially the rarer ones, but sometimes you might get some written info, or as you have found out, you can look online for side effects before making a decision. i'm afraid you are on a hiding to nothing, and if you want to persue it down a legal route, you will just be wasting your money