I don't have a 60D to check, but many cameras have semi-transparent mirrors. Are you sure that's not what you are seeing?
If in fact there is a speck of something on there, it really will do no harm. It's just a nuisance. The mirror flips up out of the way whenever the shutter is open for an exposure, so it won't show up in any photos.
If it just plain bugs you, you might ask to exchange the camera with the retailer... or have it cleaned. You can clean it yourself, but I really don't recommend inexperienced people do that. It's a bit risky because the mirror and the focus screen right above it are relatively delicate and easily damaged. It's easy to make things worse and end up with an expensive repair bill.
A blower, such as you've tried, is usually the safest thing to try yourself, and then have the camera professionally cleaned occasionally.