But you were right in the first place and BOTH of those doctors were mistaken. It is NOT an hemangioma, as they all involute before adulthood.
And other vascular birthmarks have different treatment options than hemagiomas, so it's important to get it correctly diagnosed.
It could be a vascular malformation, yes. Without something to give it some scale, it's hard to tell what size it is.
Where are you located? It's best that you see a specialist.
You could go to http://birthmark.org/experts.php
. I would write to Dr. Levitin there and send him that picture.