Accidently showed a job ad to my manager?

On friday before I left work I emailed from my work account to my personal email account internal job postings I found from the government's intranet. My boss recently created a permanent job for me because I am a temp. I did a test for it today and having interview this week if my manager still wants me anymore. I am planning to leave because I want to go back to the field I studied in (life sciences) currently I am no where in the life sciences field. I learned a lot from this job and I have a great boss but I am not interested in the field of the workplace (alcohol & gaming). Anyways he was talking to me and I was going through my outbox to show him an email but I accidently click a few times on job ads I emailed to myself. I am such a moron. This week is the interview for the perm position. At first I didn't want it but now I want it because I feel bad I betrayed my manager who created a permanent post for me.

Suggestion:

Just say you was looking incase you wasn't made permanent. Just say you need a backup plan. That way he thinks you will still be interested in the permanent job should you need it.