Good point dude. We don't really know the actual distance the rover was when it took this shot. It could have been far enough away where they didn't see it, who knows. I was working on another picture with the rover and the small people and creatures all in it, and in this it appeared you could see their wonderment and probable fear. There seems to be a variety-of-size humanoids and creatures on Mars, from very small to large like you see in our dogs and insects for example.
Now if you take a look at the post that Saintdlee put on called "Animated GIF's from Mars" you will see creatures that are probably close to our size. They are very hard to see because NASA has tried to block them out. The thing is that you can still see their outline, and with the GIF's that Saintdlee did, you can see their movements.
Also I'm including the pictures below, to give you an idea of how small some of these humanoids and creatures are. I've been looking at this for quite a while now, and you see humanoids, as well as creatures, or critters (what ever you want to call them) looking directly at the rover, some being almost directly below it. In the first picture there is a bridge with an arrow pointing at it. Under, over, and around that bridge seem to be quite a few people and critters looking at the rover. In structures farther back there are more people and critters looking at it, some from balconies. I'm guarantee you that they must be scared out of their whits!!! In the second picture is a crop from the first, and to the middle left of the picture you can see the small ones looking up. Take a gander at it and I hope you can see them. One problem here is when I put these pictures on the form I have to shrink their size and I lose a lot of detail, but I think you'll be able to see enough. I've also put the link to the original picture if you want to work it yourself:)
Cruisedad
www.midnightplanets.com/data/MERBRawJPG/04032/1N486123314EFFCNJDP1745R0M1.JPG