Watch over your GoogleAcc. Is the AutoBackup photos is on? if yes.. all the photos are there. If not you should search the phone when you conenct it with computer. Are you using a SD card? if yes, try to connect it with adapter (card reader) and watch there
Remember!
You can recover easy with your computer. Connect the phone to it and copy all the photos. You can write them to DVD if you want them to be pure safe. Asus zenphone is strong phone. You can turn ON your autobackup photos into your GoogleAcc. If you shoot something and the internet is on... the photo will be uploaded into your google acc and you cant lose them.