Armis, there is nothing to panic about as, even if you don't find the e-mail, you'll still be able to phone the airline and they will give you your booking reference and the flight details.

It is extemely unlikely that you will need to show anyone the printed e-mail and, even if it's needed, you can tell the checkin staff that you deleted it and they will still be able to check your mother in for her flight.

So please don't panic!