I was told the same thing -- but RE did a mock cycle anyway to check. My linings always got up to 11-13, but I could not get to 6 during the mock after the surgery.
I went to another RE, who I am now seeing (and who tested me for additional immune and clotting issues, which I tested positive for) and he pulled me off all the estrogen and said - we will put you on a protocol with viagra and some other things to address that lining. He said it is very common for a surgery to make it more difficult to build a lining, and he also pointed out where in the uterus he would avoid placement during transfer.
So, even though I am glad I got the surgery, I am glad I changed REs, as he is familiar with addressing this issue.
It is odd they would skip the mock after a surgery -- insist on it.
I know A LOT of gals who this happened to, and they have their little ones. You just might need some boosters.
For myself, I also plan to do a slew of things (act, walking, femoral massage, etc) to help increase blood flow.