...which was reprinted in one of those anniversary issues or annual, I can't be certain, given the volume of comics I have, and how busy I am with work (can't rummage through all of those comics)... but it clearly states that Mjolnir returns to the same spot where it was thrown, and that Thor can somehow control it's flight.
The fact that it doesn't work for you (or doesn't make sense) is really neither here nor there. Like I said, it returns to the same spot, and like I also said, he can command his hammer's flight (or summon it) if he is somehow displaced. It does not always return to his hand. How else can you explain how Thor was hit by mjolnir at the back (one of those Marvel Team-up issue with Spidey vs the Black Abbot, or some cult)? The Juggernaut once rode mjolir to hit Thor (it didn't return to his hand). Yes, most of the time it returns to his hand... that's because Thor can control it's flight. Sure he can fight multiple opponents even without his hammer, and he will find a way to get mjolnir, not because his hammer automatically return to his hand...it's really a combination of fighting skill, and the fact that he can control the hammer's flight (like how he can somehow control it's flight while grasping the thing).
And about the original post, I already answered the original poster in the affirmative, and there really is no doubt, Thor can summon the hammer, the same way he can control it's flight, etc.
Anyway, tomato-tomAto, whatever floats your boat. I can't really get into this discussion. But if I find that back-up feature explaining how Mjolnir works I will just post scans here.
It was originally stated that Mjolnir returns to the spot from which it is thrown, and perhaps this remained so until Stan Lee left. However, in later runs, it was affirmed that Mjolnir returns to Thor's hand. Thor stated the nature of the enchantment when he bluffed Loki with a threat of decapitation.