I also find it odd that you don't sell basic lands, but that doesn't excuse the kids. Good grief, shop says "no" so you try to steal the cards instead?
But yeah, judging from what Hubby said of the last prerelease he went to, Wizards doesn't actually supply the basic lands to the shops for the events, so they have to provide their own.
Hubby and I thankfully don't need to stock up on lands for now, seeing as the year we were married we inherited a huuuuge
set of cards from someone else in our complex, including a ton of basic lands. Eventually we'll have to pick up some more (mountains, apparently, last I checked), but until then....
I had a non-SC problem with Magic the Gathering, spending $120 for great cards then finding out there was nobody who lived nearby to play against. Bleah. (A case of putting the card before the horse.)
This is one reason why recently, Hubby and I have been experimenting with playing with a friend of ours over Skype. So far, not too shabby.