Children...

#1, did you pack everything you need?
Yes.
Do you want to go up to your room and do one more check?
No. It's all in there. I'm sure.
You're sure?
Yup.
You have it all?
Yes.
I'm not driving down there to deliver forgotten items.
I know. It's fine. I have everything.

Fast forward to yesterday morning.
I enter #1's bedroom to pick up and get the few remaining clothing items that need to be washed.
What is sitting in the middle of the floor?

One large blue WATER BOTTLE...

It's a good thing I love that kid enough to send it in the mail with a note that says, "Did you forget something?"