You can try putting them back together if you would like.
She may or may not accept him. Most does will refuse the male once they are pregnant, but a few will let them mate again regardless. It's not a sure fire way to tell if she's pregnant.
If the buck mounted your doe 2-3 times, the doe was lifting her rear end to receive, and the buck grunted/fell off, then she's most likely pregnant.
--Dawn