Originally Posted by Catherder:
I'd most likely send a text asking "Sorry to bother you. I can't find my check in the bag. Did it fall out in your car"
Depending on what she texts back ("yes, it did. I'll get it to you tonight, sorry." gives her a chance to save face, possibly, if she just forgot 
) I would make sure to state "DCK cannot come back without payment".
No pay no stay. 
I have one mom who forget occasionally. Since she works "in town" where my bank is, I texted her after she forgot once "could you possibly drop off the check at my bank when you're at lunch?" she said of course, since she forgot. The next time she forgot, she volunteered to do it. It's now happened 3x in 8 months. Saves me a 14 mile round trip, so yay!
She doesn't even need my bank account number, nor do I care about a receipt. I can look online anytime to make sure it got deposited ok.