Live BlackJack Dealer Makes mistake

Recently I was playing Live Blackjack. I had two hands both on 15 the dealer was showing a 7.  I chose to stand. The dealer shows 2nd card... Which is 10 .. She hastotal of 17.... She then HIT (Pulled 1 more card) herself and got another 10.. So she had a total of 27. She the says "Sorry my mistake, I have 17" and my bet gets settled as a loss.

I have reported to Betfair and they are investigating.

Has anyone experienced a similar situation?