It's simply there to give an idea of movement. You could equally well say 'sent over'. The 'down' isn't literal.

The "down" isn't important, unless the garage is someplace lower than where it us now, such as on a lower level in a building. If this isn't the situation, in the US we'd just say "sent to" in common usage.

and maybe the garage is located down the road ! for example : go down / walk down