B2 visa extension and reentry

Hello,
my mother came to usa in july 2014 and we had filed her B2 extension (electronic filing) which got approved in may 2015 which was valid until end of May. Right after the approval she left to India on May 9th 2015. She is planning to visit us next month but we lost the approval notice for B2 extension.
we only have the payment receipt which has the Receipt ID: IOE******
Will that be a problem during reentry? Does she need to have the original approval notice?

It’s advisable to get duplicate approval notice using I-824. I have seen people being asked for it even during Visa Renewal.

Thank you!
Called USCIS and they said she should be good to travel with ‘case receipt notice’ and the extension application that was filed in 2014. However, we will still apply for I-824, but they are asking $465 and processing times are 6months to 89 months !!