It's probably still raw, held together by the membrane. Boiled eggs turn white, remember.
Acetic acid is the acid in vinegar and while it is dilute, it still attacks calcium fairly aggressively owing to its chemistry.
We did this in biology this year. The last day we were supposed to throw them away so one of my friends takes the egg and walks over to the trash can and bites it. Vinegar and egg just turned practically to liquid. He gagged and everyone laughed. What a good last week of school that was.
Acetic acid is the acid in vinegar and while it is dilute, it still attacks calcium fairly aggressively owing to its chemistry.