Hi Bean, I forgot my shot one day too and ended up taking it 12 hours late. My RE said not to worry but did a blood test anyway and progesterone was normal. They tend to keep your levels a little higher than natural anyway since there is really no downside (except for YOU who have to endure the side effects--bloating, depression, etc). Anyway the bottom line: You will be FINE!!!!
my wife forgot also around the 10 day ET, and she still got a BFP. Just contact your doc and as the poster above said I think they try to keep your levels a bit higher.