Short story:  My outdoor faucet was turned on (without an attached hose) for probably 18+ hours, causing water to get into the basement and soak all of the carpet.  I spent today ripping it out and putting it outside, and throwing away all the super soaked padding.  The concrete floor is drying very nicely now.

On to my post:

 Since I can't sleep after today, I've been researching how this may have happened.  I'm feeling more confident I know how the flooding happened.  My contractor mentioned this and initially I thought it was unlikely, but after doing some web research and remembering more, it is likely.  I recently bought a new rubber O ring for my faucet to hose connection because it always leaked at the faucet.  With the new one, it doesn't leak at all which is good.  Except I got used to seeing the leak as a sign it was on.  Early in the weekend, I switched the hose end from the sprinker to a closeable nozzle.  I left the nozzle on the hose after using it, with the hose left stretched out across the yard, with plenty of it exposed to the sun.  The water was probably left on, and I didn't drain the hose like I usually do.  Monday was a hot day, which heated up the hose with a lot of surface area exposed, and likely caused a lot of pressure to build up.  I know Monday morning it wasn't burst, and Tuesday morning it was.  It must have burst at the weakest point being the hose coiler connector at the faucet sometime Monday afternoon.

 I think it was a combo of the first hot day since I got the hose fixed,  left it pressurized (closed nozzle), and left on unintentionally that caused this to happen.  I've learned you can buy pressure relief adapters to keep this from happening too.

With the hose on, this pressure may have gone back into the house a little before it burst and dripped into the washing machine (I'm not confident on that though, the washer is still a mystery).  I can't find any other leak evidence though elsewhere.