samsung galaxy s3 - device memory damaged
last night when i went to charge my battery from dead, plugged in the charger, turned the phone on and got the following message: "device memory damaged - the data partition has been corrupted. you need to reset your device to factory defaults. this will erase all of your data". i haven't backed anything up but photos seem to be on drop box. however, my diary which i had set to sync with google calendar stopped syncing about 2 months ago and so all the information i had entered onto the diary, i cannot find on google calendar and i cannot see my contacts on my google account. am i doing something wrong? is the data there but i just can't find it or has the data gone forever? and if i get a data recovery app (i know nothing about them other than they exist from having read people's posts online today), will that recover the data after a factory reset? as obviously i cannot turn the phone on to download the app without doing the factory reset first. please help me in as lay terms as possible as i am not very tech savvy.