It seems to me that this could have happened a lot of times without us knowing.
Definitely. The 1976 rock made it into a really crappy novel, I think it was called “Asteroid” (took ‘em months to come up with the title), and it wasn’t any 27 years later. So, maybe it was a different big close call. So yeah, it probably happens all the time. The smaller ones are of less concern, but it’s a bit daunting to realize that this thing is a quarter mile in diameter, and has been just missing us very few years for maybe millions of years, and wasn’t even spotted until 2005. :’)
The things that hit the Earth from time to time are probably nearly 100% nearby on a regular basis, and, like the old Spirograph toy, after enough cycles, our paths cross. A big interloper from waaaay out, or one just passing through the Solar System, could of course hit the Earth, but the odds are vanishingly small.