On my Nexus 5, with Android 5.0.1, I had switched to guest user and had taken some photos. Then I switched back to my admin user. A day after I switched back to guest user to get those photos and started a new session instead of continuing the previous session and I lost all my photos. I know starting a new session would have deleted all data of previous guest user as it is temporary data, however is there any way I can recover those photos deleted from guest account.
No, if it's right what you say and all guest data from the previous session was deleted you can't find anything back. If it isn't deleted completely you can try to look for it in the system folders.
Have a nice day,