How do you deal with this?

I have been donating since April this year. Most of the recipient moms have offered to replace the bags used and even if someone doesn't, I gently remind them and they either replace the bags or send me an equivalent amount of money later. In case I have made small donations (less than 30 bags), I myself refused the money offered for the bags.
I have had a recent experience in which someone did not replace the bags even though they said they would - after my husband spent more than 2 hours driving on a hot day for giving the milk while I stayed back home with a toddler running 102.5 fever and a 4-month old. It is not the amount of money that matters, it is the dishonesty which strikes you. It was as a child we were taught - When someone says Sorry or Thank You, Mean it or Don't say anything at all! Why would someone say we will replace the bags, pay for shipping, pay for packaging materials only to choose to not to do so when the time comes? I can understand and will even appreciate if a recipient comes and says upfront - Hey, we need your milk for our baby, but are too poor to pay for the bags/cooler etc. In this case, I know what to expect and will be happy to donate the bags along with the milk and cooler.

Anyway, coming to my original question of how to deal with this kind of situation, I decided to move on. But really, couldn't the recipients be a little bit more honest about their situation?

Could you email them and say "oh, I think my husband forgot to pick up the money/bags that you were replacing. Here's my paypal address for you to send money when you get a chance"?

Next time so you don't feel burned perhaps ask for reimbursement up front from paypal. Then you know it is taken care of.

So sorry. I hope this doesn't ruin your experience and you find a recipient who appreciates your efforts and sacrifice.

No, it didn't ruin my overall experience; as I said I moved on :-) About asking this mom for reimbursement I don't want to sound like begging. I mean, shouldn't just emailing them beforehand when we are discussing all the details be enough? and anyway, it wasn't about the money.
Thanks for the suggestion about paypal...May be something to consider in future.