2006: I buy a DS. Oh the boundless fun.

2007: DS Lite. MY God it is amazing!

Late 2007: DS Lite is lost within the house. All search attempts fail.

3 Days Ago: Found it! Does not work.

2 Days Ago: Blowing on it allows the game to play!

1 Day Ago: Still Works, but needs a crap load of blowing.

23 Minutes Ago: DS craps out. Blowing does not work.

I WANNA PLAY! Since it has been lying for months, is there dust, or is there a larger problem needing me to buy a new DS?

Oops, I need more clarification.

If I insert it, it comes to the main menu saying "No DS Card Inserted."

Sorry i can't help

Just curious, where do you found it?

Did you try multiple different games? If not try that... It could be the game...
Other then that obvious one, I'd say your DS is Deader then a dead guy.

Actually, when exposed to some water it worked.

You could always try to like, clean out the ds slot gently with a cotton swab or something, just to see if that helps^^ I'm not entirely sure, but it doesn't seem like it'd just break from dust or being lost or whatnot.

I'll try that out.

Nintendo fixes/replaces DS' for a very reasonable price.