I-94 not collected by airline during previous visit

[ramsubra]

My Mother visited US in May 2011 and left in Sept 2011. However, we realized just now , that my Mother's I-94 was not collected by airline and it is still with us. We have not retained the boarding passes . The

only proof I have is the entry stamp in passport at Mumbai Airport.

My Mother is planning an trip next month. Will there be any issues at POE ? Kindly advise .

Thanks