Ahh boo...What a let down. But I always say to myself that if they baby doesn't show then that's what's meant to be!! Wouldn't the only way your doc could know is from the u/s pics? I don't they can tell any other way unless you had an amnio done or something right?! Will they let you book another one if you really wanna know?!
I know here in BC they aren't actually allowed to tell you, they can only hint at it! I saw the 3 hamburger lines though on the ultrasound, and the tech didn't deny it was a girl, but I still went and got a 3d ultrasound done and was able to find out there for sure!
The same thing happened to me with my second pregnancy! Well, DS's legs were tight together....the tech looked for like 40 minutes but couldn't tell us for sure. I was bummed, but actually ended up being happy we didn't know, in the end....We didn't want to know with our first, and so we knew how cool it was to have that surprise.
Usually, they'll write it in the report if they know....so I'm guessing that it wouldn't be in yours. If you go for a 3D/4D u/s, you'd be more likely to see something, I'd think.